[PATCHv4] sysdeps/ieee754/soft-fp: ignore maybe-uninitialized with -O [BZ #19444]

  * with -O, -O1, -Os it fails with:

In file included from ../soft-fp/soft-fp.h:318,
                 from ../sysdeps/ieee754/soft-fp/s_fdiv.c:28:
../sysdeps/ieee754/soft-fp/s_fdiv.c: In function '__fdiv':
../soft-fp/op-2.h:98:25: error: 'R_f1' may be used uninitialized in this function [-Werror=maybe-uninitialized]
        X##_f0 = (X##_f1 << (_FP_W_TYPE_SIZE - (N)) | X##_f0 >> (N) \
                         ^~
../sysdeps/ieee754/soft-fp/s_fdiv.c:38:14: note: 'R_f1' was declared here
   FP_DECL_D (R);
              ^
../soft-fp/op-2.h:37:36: note: in definition of macro '_FP_FRAC_DECL_2'
   _FP_W_TYPE X##_f0 _FP_ZERO_INIT, X##_f1 _FP_ZERO_INIT
                                    ^
../soft-fp/double.h:95:24: note: in expansion of macro '_FP_DECL'
 # define FP_DECL_D(X)  _FP_DECL (2, X)
                        ^~~~~~~~
../sysdeps/ieee754/soft-fp/s_fdiv.c:38:3: note: in expansion of macro 'FP_DECL_D'
   FP_DECL_D (R);
   ^~~~~~~~~
../soft-fp/op-2.h:101:17: error: 'R_f0' may be used uninitialized in this function [-Werror=maybe-uninitialized]
       : (X##_f0 << (_FP_W_TYPE_SIZE - (N))) != 0)); \
                 ^~
../sysdeps/ieee754/soft-fp/s_fdiv.c:38:14: note: 'R_f0' was declared here
   FP_DECL_D (R);
              ^
../soft-fp/op-2.h:37:14: note: in definition of macro '_FP_FRAC_DECL_2'
   _FP_W_TYPE X##_f0 _FP_ZERO_INIT, X##_f1 _FP_ZERO_INIT
              ^
../soft-fp/double.h:95:24: note: in expansion of macro '_FP_DECL'
 # define FP_DECL_D(X)  _FP_DECL (2, X)
                        ^~~~~~~~
../sysdeps/ieee754/soft-fp/s_fdiv.c:38:3: note: in expansion of macro 'FP_DECL_D'
   FP_DECL_D (R);
   ^~~~~~~~~

Build tested with Yocto for ARM, AARCH64, X86, X86_64, PPC, MIPS, MIPS64
with -O, -O1, -Os.
For AARCH64 it needs one more fix in locale for -Os.

	Partial fix for [BZ #23716]
	* sysdeps/ieee754/soft-fp/s_fdiv.c: Fix build with -O

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
---
 ChangeLog                        |  4 ++++
 sysdeps/ieee754/soft-fp/s_fdiv.c | 12 ++++++++++++
 2 files changed, 16 insertions(+)
  

Thanks, committed.
  

On 01/10/2018 17:26, Martin Jansa wrote:
> ---
>  ChangeLog                        |  4 ++++
>  sysdeps/ieee754/soft-fp/s_fdiv.c | 12 ++++++++++++
>  2 files changed, 16 insertions(+)
>
> diff --git a/ChangeLog b/ChangeLog
> index 4bafeefda5..9cdf59c9ab 100644
> --- a/ChangeLog
> +++ b/ChangeLog
> @@ -1,3 +1,7 @@
> +2018-09-30  Martin Jansa  <Martin.Jansa@gmail.com>
> +	Partial fix for [BZ #23716]
> +	* sysdeps/ieee754/soft-fp/s_fdiv.c: Fix build with -O.
> +
>  2018-09-29  Martin Jansa  <Martin.Jansa@gmail.com>
>  	Partial fix for [BZ #23716]
>  	* sysdeps/ieee754/dbl-96/e_jnl.c: Fix build with -O
> diff --git a/sysdeps/ieee754/soft-fp/s_fdiv.c b/sysdeps/ieee754/soft-fp/s_fdiv.c
> index 341339f5ed..f124edd760 100644
> --- a/sysdeps/ieee754/soft-fp/s_fdiv.c
> +++ b/sysdeps/ieee754/soft-fp/s_fdiv.c
> @@ -25,6 +25,16 @@
>  #undef fdivl
>  
>  #include <math-narrow.h>
> +
> +#include <libc-diag.h>
> +/* R_f[01] are not set in cases where it is not used in packing, but the
> +   compiler does not see that it is set in all cases where it is
> +   used, resulting in warnings that it may be used uninitialized.
> +   The location of the warning differs in different versions of GCC,
> +   it may be where R is defined using a macro or it may be where the
> +   macro is defined. This happens only with -O1.  */
> +DIAG_PUSH_NEEDS_COMMENT;
> +DIAG_IGNORE_NEEDS_COMMENT (8, "-Wmaybe-uninitialized");
>  #include <soft-fp.h>
>  #include <single.h>
>  #include <double.h>
> @@ -53,4 +63,6 @@ __fdiv (double x, double y)
>    CHECK_NARROW_DIV (ret, x, y);
>    return ret;
>  }
> +DIAG_POP_NEEDS_COMMENT;
> +
>  libm_alias_float_double (div)

Hello

It would be really helpful if this fix (commit id
4a06ceea33ecc220bbfe264d8f1e74de2f04e90d) could be backported from
master to the release/2.28/master branch.

This would allow all glibc 2.28 patches to be dropped from Buildroot.

Thanks

Mark
  

On 03/01/2019 12:44, Mark Corbin wrote:
> 
> 
> On 01/10/2018 17:26, Martin Jansa wrote:
>> ---
>>  ChangeLog                        |  4 ++++
>>  sysdeps/ieee754/soft-fp/s_fdiv.c | 12 ++++++++++++
>>  2 files changed, 16 insertions(+)
>>
>> diff --git a/ChangeLog b/ChangeLog
>> index 4bafeefda5..9cdf59c9ab 100644
>> --- a/ChangeLog
>> +++ b/ChangeLog
>> @@ -1,3 +1,7 @@
>> +2018-09-30  Martin Jansa  <Martin.Jansa@gmail.com>
>> +	Partial fix for [BZ #23716]
>> +	* sysdeps/ieee754/soft-fp/s_fdiv.c: Fix build with -O.
>> +
>>  2018-09-29  Martin Jansa  <Martin.Jansa@gmail.com>
>>  	Partial fix for [BZ #23716]
>>  	* sysdeps/ieee754/dbl-96/e_jnl.c: Fix build with -O
>> diff --git a/sysdeps/ieee754/soft-fp/s_fdiv.c b/sysdeps/ieee754/soft-fp/s_fdiv.c
>> index 341339f5ed..f124edd760 100644
>> --- a/sysdeps/ieee754/soft-fp/s_fdiv.c
>> +++ b/sysdeps/ieee754/soft-fp/s_fdiv.c
>> @@ -25,6 +25,16 @@
>>  #undef fdivl
>>  
>>  #include <math-narrow.h>
>> +
>> +#include <libc-diag.h>
>> +/* R_f[01] are not set in cases where it is not used in packing, but the
>> +   compiler does not see that it is set in all cases where it is
>> +   used, resulting in warnings that it may be used uninitialized.
>> +   The location of the warning differs in different versions of GCC,
>> +   it may be where R is defined using a macro or it may be where the
>> +   macro is defined. This happens only with -O1.  */
>> +DIAG_PUSH_NEEDS_COMMENT;
>> +DIAG_IGNORE_NEEDS_COMMENT (8, "-Wmaybe-uninitialized");
>>  #include <soft-fp.h>
>>  #include <single.h>
>>  #include <double.h>
>> @@ -53,4 +63,6 @@ __fdiv (double x, double y)
>>    CHECK_NARROW_DIV (ret, x, y);
>>    return ret;
>>  }
>> +DIAG_POP_NEEDS_COMMENT;
>> +
>>  libm_alias_float_double (div)
> 
> Hello
> 
> It would be really helpful if this fix (commit id
> 4a06ceea33ecc220bbfe264d8f1e74de2f04e90d) could be backported from
> master to the release/2.28/master branch.
> 
> This would allow all glibc 2.28 patches to be dropped from Buildroot.
> 
> Thanks
> 
> Mark
> 

Done.