| Message ID | 20180919100825.22999-2-Martin.Jansa@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [1/2] sysdeps/ieee754: prevent maybe-uninitialized errors | expand |
On Wed, 19 Sep 2018, Martin Jansa wrote: > diff --git a/soft-fp/op-2.h b/soft-fp/op-2.h > index 6020d663d4..6672337949 100644 > --- a/soft-fp/op-2.h > +++ b/soft-fp/op-2.h > @@ -92,6 +92,8 @@ > X##_f1 = 0; \ > })) > > +#pragma GCC diagnostic push > +#pragma GCC diagnostic ignored "-Wmaybe-uninitialized" As soft-fp is shared with libgcc, it can't use the DIAG_* macros from libc-diag.h. *But* the principle of needing detailed comments to justify any warning suppression remains. Those comments would need to identify the warning in question, and why it is a false positive, and the most recent compiler version known to produce that false positive, and the suppression should probably be conditional on building with -O if it isn't needed with -O2 / -Os. Rather than putting the suppression around a macro definition, I wonder about putting it at the place where the macros are used (s_fdiv.c, it appears from the warnings you quote). That's what we do for the soft-fp implementations of fma, for example, and it would allow you to use the DIAG_* macros. You'd need to add DIAG_IGNORE_O1_NEEDS_COMMENT like DIAG_IGNORE_Os_NEEDS_COMMENT to libc-diag.h, and then use it with an appropriate comment in s_fdiv.c (explaining the warning and why it is a false positive).
diff --git a/soft-fp/op-2.h b/soft-fp/op-2.h index 6020d663d4..6672337949 100644 --- a/soft-fp/op-2.h +++ b/soft-fp/op-2.h @@ -92,6 +92,8 @@ X##_f1 = 0; \ })) +#pragma GCC diagnostic push +#pragma GCC diagnostic ignored "-Wmaybe-uninitialized" #define _FP_FRAC_SRS_2(X, N, sz) \ (void) (((N) < _FP_W_TYPE_SIZE) \ ? ({ \ @@ -109,6 +111,7 @@ | X##_f0) != 0)); \ X##_f1 = 0; \ })) +#pragma GCC diagnostic pop #define _FP_FRAC_ADDI_2(X, I) \ __FP_FRAC_ADDI_2 (X##_f1, X##_f0, I)
* with -O 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); ^~~~~~~~~ Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com> --- soft-fp/op-2.h | 3 +++ 1 file changed, 3 insertions(+)