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[edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()

Laszlo Ersek posted 2 patches 7 years, 3 months ago
[edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Laszlo Ersek 7 years, 3 months ago 
When building the driver for DEBUG/RELEASE, GCC48/GCC49 warn about
ReadFile() possibly using "BytesLeft" without initializing it first.

This is not the case. The reads of "BytesLeft" are only reachable if
(ReadFileInfo->Flags == READ_FILE_SEEK_AND_READ). But, in that case, we
also set "BytesLeft" to "ReadFileInfo->FileDataSize", near the top of the
function.

Assign "BytesLeft" zero at the top, and add a comment that conforms to the
pending Coding Style Spec feature request at
<https://bugzilla.tianocore.org/show_bug.cgi?id=607>.

This issue was reported by Ard's and Gerd's CI systems independently.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Paulo Alcantara <pcacjr@zytor.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reported-by: Gerd Hoffmann <kraxel@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c b/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
index 096fbb4452cb..392494b2eb3f 100644
--- a/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
+++ b/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
@@ -893,6 +893,11 @@ ReadFile (
   LogicalBlockSize  = LV_BLOCK_SIZE (Volume, UDF_DEFAULT_LV_NUM);
   DoFreeAed         = FALSE;
 
+  //
+  // set BytesLeft to suppress incorrect compiler/analyzer warnings
+  //
+  BytesLeft = 0;
+
   switch (ReadFileInfo->Flags) {
   case READ_FILE_GET_FILESIZE:
   case READ_FILE_ALLOCATE_AND_READ:
-- 
2.14.1.3.gb7cf6e02401b

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Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Zeng, Star 7 years, 3 months ago 
Reviewed-by: Star Zeng <star.zeng@intel.com>

-----Original Message-----
From: Laszlo Ersek [mailto:lersek@redhat.com] 
Sent: Wednesday, September 13, 2017 6:26 AM
To: edk2-devel-01 <edk2-devel@lists.01.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>; Dong, Eric <eric.dong@intel.com>; Paulo Alcantara <pcacjr@zytor.com>; Ni, Ruiyu <ruiyu.ni@intel.com>; Zeng, Star <star.zeng@intel.com>
Subject: [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()

When building the driver for DEBUG/RELEASE, GCC48/GCC49 warn about
ReadFile() possibly using "BytesLeft" without initializing it first.

This is not the case. The reads of "BytesLeft" are only reachable if (ReadFileInfo->Flags == READ_FILE_SEEK_AND_READ). But, in that case, we also set "BytesLeft" to "ReadFileInfo->FileDataSize", near the top of the function.

Assign "BytesLeft" zero at the top, and add a comment that conforms to the pending Coding Style Spec feature request at <https://bugzilla.tianocore.org/show_bug.cgi?id=607>.

This issue was reported by Ard's and Gerd's CI systems independently.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Paulo Alcantara <pcacjr@zytor.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reported-by: Gerd Hoffmann <kraxel@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c b/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
index 096fbb4452cb..392494b2eb3f 100644
--- a/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
+++ b/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
@@ -893,6 +893,11 @@ ReadFile (
   LogicalBlockSize  = LV_BLOCK_SIZE (Volume, UDF_DEFAULT_LV_NUM);
   DoFreeAed         = FALSE;
 
+  //
+  // set BytesLeft to suppress incorrect compiler/analyzer warnings  //  
+ BytesLeft = 0;
+
   switch (ReadFileInfo->Flags) {
   case READ_FILE_GET_FILESIZE:
   case READ_FILE_ALLOCATE_AND_READ:
--
2.14.1.3.gb7cf6e02401b

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Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Zeng, Star 7 years, 3 months ago 
Beyond the Rb (I do not want to block this patch series), I am curious about one question.

There may be more this kind of workarounds to fix the build failure.
Is it possible to disable the warning (like below example for VS) for specific version of GCC for this kind of false alarm?


ProcessorBind.h:
#if defined(_MSC_EXTENSIONS)

...

#if _MSC_VER == 1800 || _MSC_VER == 1900

//
// Disable these warnings for VS2013.
//

//
// This warning is for potentially uninitialized local variable, and it may cause false 
// positive issues in VS2013 and VS2015 build
//
#pragma warning ( disable : 4701 )
  
//
// This warning is for potentially uninitialized local pointer variable, and it may cause 
// false positive issues in VS2013 and VS2015 build
//
#pragma warning ( disable : 4703 )
  
#endif

#endif


Thanks,
Star
-----Original Message-----
From: Zeng, Star 
Sent: Wednesday, September 13, 2017 2:34 PM
To: Laszlo Ersek <lersek@redhat.com>; edk2-devel-01 <edk2-devel@lists.01.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>; Dong, Eric <eric.dong@intel.com>; Paulo Alcantara <pcacjr@zytor.com>; Ni, Ruiyu <ruiyu.ni@intel.com>; Zeng, Star <star.zeng@intel.com>
Subject: RE: [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()

Reviewed-by: Star Zeng <star.zeng@intel.com>

-----Original Message-----
From: Laszlo Ersek [mailto:lersek@redhat.com]
Sent: Wednesday, September 13, 2017 6:26 AM
To: edk2-devel-01 <edk2-devel@lists.01.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>; Dong, Eric <eric.dong@intel.com>; Paulo Alcantara <pcacjr@zytor.com>; Ni, Ruiyu <ruiyu.ni@intel.com>; Zeng, Star <star.zeng@intel.com>
Subject: [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()

When building the driver for DEBUG/RELEASE, GCC48/GCC49 warn about
ReadFile() possibly using "BytesLeft" without initializing it first.

This is not the case. The reads of "BytesLeft" are only reachable if (ReadFileInfo->Flags == READ_FILE_SEEK_AND_READ). But, in that case, we also set "BytesLeft" to "ReadFileInfo->FileDataSize", near the top of the function.

Assign "BytesLeft" zero at the top, and add a comment that conforms to the pending Coding Style Spec feature request at <https://bugzilla.tianocore.org/show_bug.cgi?id=607>.

This issue was reported by Ard's and Gerd's CI systems independently.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Paulo Alcantara <pcacjr@zytor.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reported-by: Gerd Hoffmann <kraxel@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c b/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
index 096fbb4452cb..392494b2eb3f 100644
--- a/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
+++ b/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
@@ -893,6 +893,11 @@ ReadFile (
   LogicalBlockSize  = LV_BLOCK_SIZE (Volume, UDF_DEFAULT_LV_NUM);
   DoFreeAed         = FALSE;
 
+  //
+  // set BytesLeft to suppress incorrect compiler/analyzer warnings  // 
+ BytesLeft = 0;
+
   switch (ReadFileInfo->Flags) {
   case READ_FILE_GET_FILESIZE:
   case READ_FILE_ALLOCATE_AND_READ:
--
2.14.1.3.gb7cf6e02401b

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edk2-devel@lists.01.org
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Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Laszlo Ersek 7 years, 3 months ago 
On 09/13/17 08:43, Zeng, Star wrote:
> Beyond the Rb (I do not want to block this patch series), I am curious about one question.
> 
> There may be more this kind of workarounds to fix the build failure.
> Is it possible to disable the warning (like below example for VS) for specific version of GCC for this kind of false alarm?
> 
> 
> ProcessorBind.h:
> #if defined(_MSC_EXTENSIONS)
> 
> ...
> 
> #if _MSC_VER == 1800 || _MSC_VER == 1900
> 
> //
> // Disable these warnings for VS2013.
> //
> 
> //
> // This warning is for potentially uninitialized local variable, and it may cause false 
> // positive issues in VS2013 and VS2015 build
> //
> #pragma warning ( disable : 4701 )
>   
> //
> // This warning is for potentially uninitialized local pointer variable, and it may cause 
> // false positive issues in VS2013 and VS2015 build
> //
> #pragma warning ( disable : 4703 )
>   
> #endif
> 
> #endif

I think starting with gcc-4.6, gcc supports the "diagnostics" pragma,
which can be used to suppress warnings.

Unfortunately, there's no pragma to suppress *only* the incorrect
warnings :) So if we set the pragma, we could lose even those warnings
that point out real bugs.

Thanks
Laszlo

> 
> 
> Thanks,
> Star
> -----Original Message-----
> From: Zeng, Star 
> Sent: Wednesday, September 13, 2017 2:34 PM
> To: Laszlo Ersek <lersek@redhat.com>; edk2-devel-01 <edk2-devel@lists.01.org>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>; Dong, Eric <eric.dong@intel.com>; Paulo Alcantara <pcacjr@zytor.com>; Ni, Ruiyu <ruiyu.ni@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: RE: [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
> 
> Reviewed-by: Star Zeng <star.zeng@intel.com>
> 
> -----Original Message-----
> From: Laszlo Ersek [mailto:lersek@redhat.com]
> Sent: Wednesday, September 13, 2017 6:26 AM
> To: edk2-devel-01 <edk2-devel@lists.01.org>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>; Dong, Eric <eric.dong@intel.com>; Paulo Alcantara <pcacjr@zytor.com>; Ni, Ruiyu <ruiyu.ni@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
> 
> When building the driver for DEBUG/RELEASE, GCC48/GCC49 warn about
> ReadFile() possibly using "BytesLeft" without initializing it first.
> 
> This is not the case. The reads of "BytesLeft" are only reachable if (ReadFileInfo->Flags == READ_FILE_SEEK_AND_READ). But, in that case, we also set "BytesLeft" to "ReadFileInfo->FileDataSize", near the top of the function.
> 
> Assign "BytesLeft" zero at the top, and add a comment that conforms to the pending Coding Style Spec feature request at <https://bugzilla.tianocore.org/show_bug.cgi?id=607>.
> 
> This issue was reported by Ard's and Gerd's CI systems independently.
> 
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Paulo Alcantara <pcacjr@zytor.com>
> Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> Cc: Star Zeng <star.zeng@intel.com>
> Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Reported-by: Gerd Hoffmann <kraxel@redhat.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
> ---
>  MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c b/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
> index 096fbb4452cb..392494b2eb3f 100644
> --- a/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
> +++ b/MdeModulePkg/Universal/Disk/UdfDxe/FileSystemOperations.c
> @@ -893,6 +893,11 @@ ReadFile (
>    LogicalBlockSize  = LV_BLOCK_SIZE (Volume, UDF_DEFAULT_LV_NUM);
>    DoFreeAed         = FALSE;
>  
> +  //
> +  // set BytesLeft to suppress incorrect compiler/analyzer warnings  // 
> + BytesLeft = 0;
> +
>    switch (ReadFileInfo->Flags) {
>    case READ_FILE_GET_FILESIZE:
>    case READ_FILE_ALLOCATE_AND_READ:
> --
> 2.14.1.3.gb7cf6e02401b
> 

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Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Ard Biesheuvel 7 years, 3 months ago 
On 13 September 2017 at 11:49, Laszlo Ersek <lersek@redhat.com> wrote:
> On 09/13/17 08:43, Zeng, Star wrote:
>> Beyond the Rb (I do not want to block this patch series), I am curious about one question.
>>
>> There may be more this kind of workarounds to fix the build failure.
>> Is it possible to disable the warning (like below example for VS) for specific version of GCC for this kind of false alarm?
>>
>>
>> ProcessorBind.h:
>> #if defined(_MSC_EXTENSIONS)
>>
>> ...
>>
>> #if _MSC_VER == 1800 || _MSC_VER == 1900
>>
>> //
>> // Disable these warnings for VS2013.
>> //
>>
>> //
>> // This warning is for potentially uninitialized local variable, and it may cause false
>> // positive issues in VS2013 and VS2015 build
>> //
>> #pragma warning ( disable : 4701 )
>>
>> //
>> // This warning is for potentially uninitialized local pointer variable, and it may cause
>> // false positive issues in VS2013 and VS2015 build
>> //
>> #pragma warning ( disable : 4703 )
>>
>> #endif
>>
>> #endif
>
> I think starting with gcc-4.6, gcc supports the "diagnostics" pragma,
> which can be used to suppress warnings.
>
> Unfortunately, there's no pragma to suppress *only* the incorrect
> warnings :) So if we set the pragma, we could lose even those warnings
> that point out real bugs.
>

That applies to the VS case as well. But I think doing this for older
GCCs is fine, most EDK2 developers use a newer version anyway, so we
will not lose any coverage by doing so.
_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
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Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Zeng, Star 7 years, 3 months ago 
Comparing adding workaround in code with suppressing it in *OLD* version GCCs, I prefer the latter personally.


Thanks,
Star
-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Ard Biesheuvel
Sent: Thursday, September 14, 2017 2:52 AM
To: Laszlo Ersek <lersek@redhat.com>
Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
Subject: Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()

On 13 September 2017 at 11:49, Laszlo Ersek <lersek@redhat.com> wrote:
> On 09/13/17 08:43, Zeng, Star wrote:
>> Beyond the Rb (I do not want to block this patch series), I am curious about one question.
>>
>> There may be more this kind of workarounds to fix the build failure.
>> Is it possible to disable the warning (like below example for VS) for specific version of GCC for this kind of false alarm?
>>
>>
>> ProcessorBind.h:
>> #if defined(_MSC_EXTENSIONS)
>>
>> ...
>>
>> #if _MSC_VER == 1800 || _MSC_VER == 1900
>>
>> //
>> // Disable these warnings for VS2013.
>> //
>>
>> //
>> // This warning is for potentially uninitialized local variable, and 
>> it may cause false // positive issues in VS2013 and VS2015 build // 
>> #pragma warning ( disable : 4701 )
>>
>> //
>> // This warning is for potentially uninitialized local pointer 
>> variable, and it may cause // false positive issues in VS2013 and 
>> VS2015 build // #pragma warning ( disable : 4703 )
>>
>> #endif
>>
>> #endif
>
> I think starting with gcc-4.6, gcc supports the "diagnostics" pragma, 
> which can be used to suppress warnings.
>
> Unfortunately, there's no pragma to suppress *only* the incorrect 
> warnings :) So if we set the pragma, we could lose even those warnings 
> that point out real bugs.
>

That applies to the VS case as well. But I think doing this for older GCCs is fine, most EDK2 developers use a newer version anyway, so we will not lose any coverage by doing so.
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Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Zeng, Star 7 years, 3 months ago 
Seemingly, VS has similar issue with GCC.

VS2010/VS2012 still have the building failures below after this patch. :(
edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1083) : error C2220: warning treated as error - no 'executable' file generated
edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1083) : warning C4701: potentially uninitialized local variable 'FilePosition' used
edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1078) : warning C4701: potentially uninitialized local variable 'FinishedSeeking' used
edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1167) : warning C4701: potentially uninitialized local variable 'Data' used
edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1167) : warning C4703: potentially uninitialized local pointer variable 'Data' used


Liming, Dandan and Hao,
Do you remember how we fix this kind of false alarm before?
Just initialize the variable at the beginning of the function?



Thanks,
Star
-----Original Message-----
From: Zeng, Star 
Sent: Thursday, September 14, 2017 8:43 AM
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>; Laszlo Ersek <lersek@redhat.com>
Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
Subject: RE: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()

Comparing adding workaround in code with suppressing it in *OLD* version GCCs, I prefer the latter personally.


Thanks,
Star
-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Ard Biesheuvel
Sent: Thursday, September 14, 2017 2:52 AM
To: Laszlo Ersek <lersek@redhat.com>
Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
Subject: Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()

On 13 September 2017 at 11:49, Laszlo Ersek <lersek@redhat.com> wrote:
> On 09/13/17 08:43, Zeng, Star wrote:
>> Beyond the Rb (I do not want to block this patch series), I am curious about one question.
>>
>> There may be more this kind of workarounds to fix the build failure.
>> Is it possible to disable the warning (like below example for VS) for specific version of GCC for this kind of false alarm?
>>
>>
>> ProcessorBind.h:
>> #if defined(_MSC_EXTENSIONS)
>>
>> ...
>>
>> #if _MSC_VER == 1800 || _MSC_VER == 1900
>>
>> //
>> // Disable these warnings for VS2013.
>> //
>>
>> //
>> // This warning is for potentially uninitialized local variable, and 
>> it may cause false // positive issues in VS2013 and VS2015 build // 
>> #pragma warning ( disable : 4701 )
>>
>> //
>> // This warning is for potentially uninitialized local pointer 
>> variable, and it may cause // false positive issues in VS2013 and
>> VS2015 build // #pragma warning ( disable : 4703 )
>>
>> #endif
>>
>> #endif
>
> I think starting with gcc-4.6, gcc supports the "diagnostics" pragma, 
> which can be used to suppress warnings.
>
> Unfortunately, there's no pragma to suppress *only* the incorrect 
> warnings :) So if we set the pragma, we could lose even those warnings 
> that point out real bugs.
>

That applies to the VS case as well. But I think doing this for older GCCs is fine, most EDK2 developers use a newer version anyway, so we will not lose any coverage by doing so.
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Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Gao, Liming 7 years, 3 months ago 
Right. Just initialize them. They are not reported in VS2013&VS2015, because VS2013 and VS2015 disables this warning in ProcessorBind.h. If they are all false warning messages, I think we can propose to disable this warning for all VS tool chain. 

For GCC, if this warning is also false, could we add compiler to disable it, like -Wno-unused-but-set-variable.

> -----Original Message-----
> From: Zeng, Star
> Sent: Thursday, September 14, 2017 9:21 AM
> To: Ard Biesheuvel <ard.biesheuvel@linaro.org>; Laszlo Ersek <lersek@redhat.com>; Gao, Liming <liming.gao@intel.com>; Bi, Dandan
> <dandan.bi@intel.com>; Wu, Hao A <hao.a.wu@intel.com>
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>
> Subject: RE: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
> 
> Seemingly, VS has similar issue with GCC.
> 
> VS2010/VS2012 still have the building failures below after this patch. :(
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1083) : error C2220: warning treated as error - no 'executable' file
> generated
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1083) : warning C4701: potentially uninitialized local variable
> 'FilePosition' used
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1078) : warning C4701: potentially uninitialized local variable
> 'FinishedSeeking' used
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1167) : warning C4701: potentially uninitialized local variable
> 'Data' used
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1167) : warning C4703: potentially uninitialized local pointer
> variable 'Data' used
> 
> 
> Liming, Dandan and Hao,
> Do you remember how we fix this kind of false alarm before?
> Just initialize the variable at the beginning of the function?
> 
> 
> 
> Thanks,
> Star
> -----Original Message-----
> From: Zeng, Star
> Sent: Thursday, September 14, 2017 8:43 AM
> To: Ard Biesheuvel <ard.biesheuvel@linaro.org>; Laszlo Ersek <lersek@redhat.com>
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming
> <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: RE: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
> 
> Comparing adding workaround in code with suppressing it in *OLD* version GCCs, I prefer the latter personally.
> 
> 
> Thanks,
> Star
> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Ard Biesheuvel
> Sent: Thursday, September 14, 2017 2:52 AM
> To: Laszlo Ersek <lersek@redhat.com>
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming
> <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
> 
> On 13 September 2017 at 11:49, Laszlo Ersek <lersek@redhat.com> wrote:
> > On 09/13/17 08:43, Zeng, Star wrote:
> >> Beyond the Rb (I do not want to block this patch series), I am curious about one question.
> >>
> >> There may be more this kind of workarounds to fix the build failure.
> >> Is it possible to disable the warning (like below example for VS) for specific version of GCC for this kind of false alarm?
> >>
> >>
> >> ProcessorBind.h:
> >> #if defined(_MSC_EXTENSIONS)
> >>
> >> ...
> >>
> >> #if _MSC_VER == 1800 || _MSC_VER == 1900
> >>
> >> //
> >> // Disable these warnings for VS2013.
> >> //
> >>
> >> //
> >> // This warning is for potentially uninitialized local variable, and
> >> it may cause false // positive issues in VS2013 and VS2015 build //
> >> #pragma warning ( disable : 4701 )
> >>
> >> //
> >> // This warning is for potentially uninitialized local pointer
> >> variable, and it may cause // false positive issues in VS2013 and
> >> VS2015 build // #pragma warning ( disable : 4703 )
> >>
> >> #endif
> >>
> >> #endif
> >
> > I think starting with gcc-4.6, gcc supports the "diagnostics" pragma,
> > which can be used to suppress warnings.
> >
> > Unfortunately, there's no pragma to suppress *only* the incorrect
> > warnings :) So if we set the pragma, we could lose even those warnings
> > that point out real bugs.
> >
> 
> That applies to the VS case as well. But I think doing this for older GCCs is fine, most EDK2 developers use a newer version anyway, so
> we will not lose any coverage by doing so.
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel
_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel
Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Laszlo Ersek 7 years, 3 months ago 
On 09/14/17 03:20, Zeng, Star wrote:
> Seemingly, VS has similar issue with GCC.
> 
> VS2010/VS2012 still have the building failures below after this patch. :(
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1083) : error C2220: warning treated as error - no 'executable' file generated
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1083) : warning C4701: potentially uninitialized local variable 'FilePosition' used
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1078) : warning C4701: potentially uninitialized local variable 'FinishedSeeking' used
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1167) : warning C4701: potentially uninitialized local variable 'Data' used
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1167) : warning C4703: potentially uninitialized local pointer variable 'Data' used
> 
> 
> Liming, Dandan and Hao,
> Do you remember how we fix this kind of false alarm before?
> Just initialize the variable at the beginning of the function?

I think that all such warnings should be evaluated carefully.

Can you please file a TianoCore BZ about the above? Paulo might want to
take a look.

Thanks!
Laszlo


> -----Original Message-----
> From: Zeng, Star 
> Sent: Thursday, September 14, 2017 8:43 AM
> To: Ard Biesheuvel <ard.biesheuvel@linaro.org>; Laszlo Ersek <lersek@redhat.com>
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: RE: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
> 
> Comparing adding workaround in code with suppressing it in *OLD* version GCCs, I prefer the latter personally.
> 
> 
> Thanks,
> Star
> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Ard Biesheuvel
> Sent: Thursday, September 14, 2017 2:52 AM
> To: Laszlo Ersek <lersek@redhat.com>
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
> 
> On 13 September 2017 at 11:49, Laszlo Ersek <lersek@redhat.com> wrote:
>> On 09/13/17 08:43, Zeng, Star wrote:
>>> Beyond the Rb (I do not want to block this patch series), I am curious about one question.
>>>
>>> There may be more this kind of workarounds to fix the build failure.
>>> Is it possible to disable the warning (like below example for VS) for specific version of GCC for this kind of false alarm?
>>>
>>>
>>> ProcessorBind.h:
>>> #if defined(_MSC_EXTENSIONS)
>>>
>>> ...
>>>
>>> #if _MSC_VER == 1800 || _MSC_VER == 1900
>>>
>>> //
>>> // Disable these warnings for VS2013.
>>> //
>>>
>>> //
>>> // This warning is for potentially uninitialized local variable, and 
>>> it may cause false // positive issues in VS2013 and VS2015 build // 
>>> #pragma warning ( disable : 4701 )
>>>
>>> //
>>> // This warning is for potentially uninitialized local pointer 
>>> variable, and it may cause // false positive issues in VS2013 and
>>> VS2015 build // #pragma warning ( disable : 4703 )
>>>
>>> #endif
>>>
>>> #endif
>>
>> I think starting with gcc-4.6, gcc supports the "diagnostics" pragma, 
>> which can be used to suppress warnings.
>>
>> Unfortunately, there's no pragma to suppress *only* the incorrect 
>> warnings :) So if we set the pragma, we could lose even those warnings 
>> that point out real bugs.
>>
> 
> That applies to the VS case as well. But I think doing this for older GCCs is fine, most EDK2 developers use a newer version anyway, so we will not lose any coverage by doing so.
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel
> 

_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel
Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Zeng, Star 7 years, 3 months ago 
It seems generic compiler issue to have this kind of false alarm.
And it seems hard decision to disable the warning for all the compilers.
We'd better to fix the build failure first, I will submit patch that will use similar method with this patch.


Thanks,
Star
-----Original Message-----
From: Laszlo Ersek [mailto:lersek@redhat.com] 
Sent: Thursday, September 14, 2017 4:20 PM
To: Zeng, Star <star.zeng@intel.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>; Gao, Liming <liming.gao@intel.com>; Bi, Dandan <dandan.bi@intel.com>; Wu, Hao A <hao.a.wu@intel.com>
Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>; Paulo Alcantara <pcacjr@zytor.com>
Subject: Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()

On 09/14/17 03:20, Zeng, Star wrote:
> Seemingly, VS has similar issue with GCC.
> 
> VS2010/VS2012 still have the building failures below after this patch. 
> :(
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1083) : 
> error C2220: warning treated as error - no 'executable' file generated
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1083) : 
> warning C4701: potentially uninitialized local variable 'FilePosition' 
> used
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1078) : 
> warning C4701: potentially uninitialized local variable 
> 'FinishedSeeking' used
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1167) : 
> warning C4701: potentially uninitialized local variable 'Data' used
> edk2\mdemodulepkg\universal\disk\udfdxe\filesystemoperations.c(1167) : 
> warning C4703: potentially uninitialized local pointer variable 'Data' 
> used
> 
> 
> Liming, Dandan and Hao,
> Do you remember how we fix this kind of false alarm before?
> Just initialize the variable at the beginning of the function?

I think that all such warnings should be evaluated carefully.

Can you please file a TianoCore BZ about the above? Paulo might want to take a look.

Thanks!
Laszlo


> -----Original Message-----
> From: Zeng, Star
> Sent: Thursday, September 14, 2017 8:43 AM
> To: Ard Biesheuvel <ard.biesheuvel@linaro.org>; Laszlo Ersek 
> <lersek@redhat.com>
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; 
> edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming 
> <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: RE: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress 
> incorrect compiler warning in ReadFile()
> 
> Comparing adding workaround in code with suppressing it in *OLD* version GCCs, I prefer the latter personally.
> 
> 
> Thanks,
> Star
> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of 
> Ard Biesheuvel
> Sent: Thursday, September 14, 2017 2:52 AM
> To: Laszlo Ersek <lersek@redhat.com>
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; 
> edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming 
> <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress 
> incorrect compiler warning in ReadFile()
> 
> On 13 September 2017 at 11:49, Laszlo Ersek <lersek@redhat.com> wrote:
>> On 09/13/17 08:43, Zeng, Star wrote:
>>> Beyond the Rb (I do not want to block this patch series), I am curious about one question.
>>>
>>> There may be more this kind of workarounds to fix the build failure.
>>> Is it possible to disable the warning (like below example for VS) for specific version of GCC for this kind of false alarm?
>>>
>>>
>>> ProcessorBind.h:
>>> #if defined(_MSC_EXTENSIONS)
>>>
>>> ...
>>>
>>> #if _MSC_VER == 1800 || _MSC_VER == 1900
>>>
>>> //
>>> // Disable these warnings for VS2013.
>>> //
>>>
>>> //
>>> // This warning is for potentially uninitialized local variable, and 
>>> it may cause false // positive issues in VS2013 and VS2015 build // 
>>> #pragma warning ( disable : 4701 )
>>>
>>> //
>>> // This warning is for potentially uninitialized local pointer 
>>> variable, and it may cause // false positive issues in VS2013 and
>>> VS2015 build // #pragma warning ( disable : 4703 )
>>>
>>> #endif
>>>
>>> #endif
>>
>> I think starting with gcc-4.6, gcc supports the "diagnostics" pragma, 
>> which can be used to suppress warnings.
>>
>> Unfortunately, there's no pragma to suppress *only* the incorrect 
>> warnings :) So if we set the pragma, we could lose even those 
>> warnings that point out real bugs.
>>
> 
> That applies to the VS case as well. But I think doing this for older GCCs is fine, most EDK2 developers use a newer version anyway, so we will not lose any coverage by doing so.
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel
> 

_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel
Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Laszlo Ersek 7 years, 3 months ago 
On 09/14/17 02:42, Zeng, Star wrote:
> Comparing adding workaround in code with suppressing it in *OLD* version GCCs, I prefer the latter personally.

But, how old is old?

The base compiler in RHEL-7 is gcc-4.8. That's what I use every day.

The base compiler in Debian old-old-stable (still supported), is gcc-4.7
(for IA32 and X64).

The base compiler in RHEL-6 (still supported) is gcc-4.4. Is that old?

Thanks
Laszlo

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Ard Biesheuvel
> Sent: Thursday, September 14, 2017 2:52 AM
> To: Laszlo Ersek <lersek@redhat.com>
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
> 
> On 13 September 2017 at 11:49, Laszlo Ersek <lersek@redhat.com> wrote:
>> On 09/13/17 08:43, Zeng, Star wrote:
>>> Beyond the Rb (I do not want to block this patch series), I am curious about one question.
>>>
>>> There may be more this kind of workarounds to fix the build failure.
>>> Is it possible to disable the warning (like below example for VS) for specific version of GCC for this kind of false alarm?
>>>
>>>
>>> ProcessorBind.h:
>>> #if defined(_MSC_EXTENSIONS)
>>>
>>> ...
>>>
>>> #if _MSC_VER == 1800 || _MSC_VER == 1900
>>>
>>> //
>>> // Disable these warnings for VS2013.
>>> //
>>>
>>> //
>>> // This warning is for potentially uninitialized local variable, and 
>>> it may cause false // positive issues in VS2013 and VS2015 build // 
>>> #pragma warning ( disable : 4701 )
>>>
>>> //
>>> // This warning is for potentially uninitialized local pointer 
>>> variable, and it may cause // false positive issues in VS2013 and 
>>> VS2015 build // #pragma warning ( disable : 4703 )
>>>
>>> #endif
>>>
>>> #endif
>>
>> I think starting with gcc-4.6, gcc supports the "diagnostics" pragma, 
>> which can be used to suppress warnings.
>>
>> Unfortunately, there's no pragma to suppress *only* the incorrect 
>> warnings :) So if we set the pragma, we could lose even those warnings 
>> that point out real bugs.
>>
> 
> That applies to the VS case as well. But I think doing this for older GCCs is fine, most EDK2 developers use a newer version anyway, so we will not lose any coverage by doing so.
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel
> 

_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel
Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Zeng, Star 7 years, 3 months ago 
Is there GCC compiler version fixed this kind of false alarm?
If yes, the lesser versions without fix are what I mean *OLD*.


Thanks,
Star
-----Original Message-----
From: Laszlo Ersek [mailto:lersek@redhat.com] 
Sent: Thursday, September 14, 2017 4:17 PM
To: Zeng, Star <star.zeng@intel.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming <liming.gao@intel.com>
Subject: Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()

On 09/14/17 02:42, Zeng, Star wrote:
> Comparing adding workaround in code with suppressing it in *OLD* version GCCs, I prefer the latter personally.

But, how old is old?

The base compiler in RHEL-7 is gcc-4.8. That's what I use every day.

The base compiler in Debian old-old-stable (still supported), is gcc-4.7 (for IA32 and X64).

The base compiler in RHEL-6 (still supported) is gcc-4.4. Is that old?

Thanks
Laszlo

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of 
> Ard Biesheuvel
> Sent: Thursday, September 14, 2017 2:52 AM
> To: Laszlo Ersek <lersek@redhat.com>
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; 
> edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming 
> <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress 
> incorrect compiler warning in ReadFile()
> 
> On 13 September 2017 at 11:49, Laszlo Ersek <lersek@redhat.com> wrote:
>> On 09/13/17 08:43, Zeng, Star wrote:
>>> Beyond the Rb (I do not want to block this patch series), I am curious about one question.
>>>
>>> There may be more this kind of workarounds to fix the build failure.
>>> Is it possible to disable the warning (like below example for VS) for specific version of GCC for this kind of false alarm?
>>>
>>>
>>> ProcessorBind.h:
>>> #if defined(_MSC_EXTENSIONS)
>>>
>>> ...
>>>
>>> #if _MSC_VER == 1800 || _MSC_VER == 1900
>>>
>>> //
>>> // Disable these warnings for VS2013.
>>> //
>>>
>>> //
>>> // This warning is for potentially uninitialized local variable, and 
>>> it may cause false // positive issues in VS2013 and VS2015 build // 
>>> #pragma warning ( disable : 4701 )
>>>
>>> //
>>> // This warning is for potentially uninitialized local pointer 
>>> variable, and it may cause // false positive issues in VS2013 and
>>> VS2015 build // #pragma warning ( disable : 4703 )
>>>
>>> #endif
>>>
>>> #endif
>>
>> I think starting with gcc-4.6, gcc supports the "diagnostics" pragma, 
>> which can be used to suppress warnings.
>>
>> Unfortunately, there's no pragma to suppress *only* the incorrect 
>> warnings :) So if we set the pragma, we could lose even those 
>> warnings that point out real bugs.
>>
> 
> That applies to the VS case as well. But I think doing this for older GCCs is fine, most EDK2 developers use a newer version anyway, so we will not lose any coverage by doing so.
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel
> 

_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel
Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
Posted by Laszlo Ersek 7 years, 3 months ago 
On 09/14/17 10:50, Zeng, Star wrote:
> Is there GCC compiler version fixed this kind of false alarm?
> If yes, the lesser versions without fix are what I mean *OLD*.

Unfortunately, I cannot answer your question, for two reasons:

- First, I'm unsure what you mean by "lesser version". For example, if
gcc-4.8.4 emits a warning incorrectly, but gcc-4.8.5 does not, then I
agree we can require users to use gcc-4.8.5. Linux distributions
consider this a "stable update" anyway, and will generally ship the
version with the higher "patch level". (The version number comes
together from <major>.<minor>.<patchlevel>.)

However, if the same difference is between gcc-4.7 and gcc-4.8, then the
same requirement cannot be made. Distros will not upgrade gcc from one
minor version to another in a stable release.

- Second, even if I knew how exactly to interpret your question, I can't
answer! The way the warnings change in gcc over time is totally
impenetrable to the end-user. The data flow analysis is tied to the
optimizer AFAICT, and unless you are a gcc developer yourself, the
warning changes appear simply as chaos, from release to release. In
practice, new releases will stop emitting invalid warnings that earlier
releases used to, but the new release may also emit new incorrect
warnings. (I.e., it might emit the *same kind* of warning, incorrectly,
for a new kind of *context*.)

Laszlo


> -----Original Message-----
> From: Laszlo Ersek [mailto:lersek@redhat.com] 
> Sent: Thursday, September 14, 2017 4:17 PM
> To: Zeng, Star <star.zeng@intel.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming <liming.gao@intel.com>
> Subject: Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress incorrect compiler warning in ReadFile()
> 
> On 09/14/17 02:42, Zeng, Star wrote:
>> Comparing adding workaround in code with suppressing it in *OLD* version GCCs, I prefer the latter personally.
> 
> But, how old is old?
> 
> The base compiler in RHEL-7 is gcc-4.8. That's what I use every day.
> 
> The base compiler in Debian old-old-stable (still supported), is gcc-4.7 (for IA32 and X64).
> 
> The base compiler in RHEL-6 (still supported) is gcc-4.4. Is that old?
> 
> Thanks
> Laszlo
> 
>> -----Original Message-----
>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of 
>> Ard Biesheuvel
>> Sent: Thursday, September 14, 2017 2:52 AM
>> To: Laszlo Ersek <lersek@redhat.com>
>> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Dong, Eric <eric.dong@intel.com>; 
>> edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming 
>> <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
>> Subject: Re: [edk2] [PATCH 2/2] MdeModulePkg/UdfDxe: suppress 
>> incorrect compiler warning in ReadFile()
>>
>> On 13 September 2017 at 11:49, Laszlo Ersek <lersek@redhat.com> wrote:
>>> On 09/13/17 08:43, Zeng, Star wrote:
>>>> Beyond the Rb (I do not want to block this patch series), I am curious about one question.
>>>>
>>>> There may be more this kind of workarounds to fix the build failure.
>>>> Is it possible to disable the warning (like below example for VS) for specific version of GCC for this kind of false alarm?
>>>>
>>>>
>>>> ProcessorBind.h:
>>>> #if defined(_MSC_EXTENSIONS)
>>>>
>>>> ...
>>>>
>>>> #if _MSC_VER == 1800 || _MSC_VER == 1900
>>>>
>>>> //
>>>> // Disable these warnings for VS2013.
>>>> //
>>>>
>>>> //
>>>> // This warning is for potentially uninitialized local variable, and 
>>>> it may cause false // positive issues in VS2013 and VS2015 build // 
>>>> #pragma warning ( disable : 4701 )
>>>>
>>>> //
>>>> // This warning is for potentially uninitialized local pointer 
>>>> variable, and it may cause // false positive issues in VS2013 and
>>>> VS2015 build // #pragma warning ( disable : 4703 )
>>>>
>>>> #endif
>>>>
>>>> #endif
>>>
>>> I think starting with gcc-4.6, gcc supports the "diagnostics" pragma, 
>>> which can be used to suppress warnings.
>>>
>>> Unfortunately, there's no pragma to suppress *only* the incorrect 
>>> warnings :) So if we set the pragma, we could lose even those 
>>> warnings that point out real bugs.
>>>
>>
>> That applies to the VS case as well. But I think doing this for older GCCs is fine, most EDK2 developers use a newer version anyway, so we will not lose any coverage by doing so.
>> _______________________________________________
>> edk2-devel mailing list
>> edk2-devel@lists.01.org
>> https://lists.01.org/mailman/listinfo/edk2-devel
>>
> 

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