Message ID | 20180930155305.19266-1-Martin.Jansa@gmail.com |
---|---|
State | New |
Headers | show |
Series | [PATCHv2] sysdeps/ieee754/soft-fp: ignore maybe-uninitialized with -O [BZ #19444] | expand |
On Sun, 30 Sep 2018, Martin Jansa wrote: > +#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 comment is missing the key information that it's specifically a warning seen with -O1.
On Sun, Sep 30, 2018 at 04:53:36PM +0000, Joseph Myers wrote: > On Sun, 30 Sep 2018, Martin Jansa wrote: > > > +#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 comment is missing the key information that it's specifically a > warning seen with -O1. The other 3 cases of the same: https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/ieee754/soft-fp/s_fma.c;h=41cf81a74bfc6a8c21c565fb04c90ced4bfd19e8;hb=refs/heads/master#l32 https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/ieee754/soft-fp/s_fmaf.c;h=afe64356b3a9c5f3467c35b80f33ba946fbeee46;hb=refs/heads/master#l32 https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/ieee754/soft-fp/s_fmal.c;h=4c2d4c5d9be09f0c8464fb20b81af3aff131e65d;hb=refs/heads/master#l32 are probably also triggered only with -O1, do you want me to update all 4 or just the new case?
On Sun, 30 Sep 2018, Martin Jansa wrote: > On Sun, Sep 30, 2018 at 04:53:36PM +0000, Joseph Myers wrote: > > On Sun, 30 Sep 2018, Martin Jansa wrote: > > > > > +#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 comment is missing the key information that it's specifically a > > warning seen with -O1. > > The other 3 cases of the same: > https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/ieee754/soft-fp/s_fma.c;h=41cf81a74bfc6a8c21c565fb04c90ced4bfd19e8;hb=refs/heads/master#l32 > https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/ieee754/soft-fp/s_fmaf.c;h=afe64356b3a9c5f3467c35b80f33ba946fbeee46;hb=refs/heads/master#l32 > https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/ieee754/soft-fp/s_fmal.c;h=4c2d4c5d9be09f0c8464fb20b81af3aff131e65d;hb=refs/heads/master#l32 > > are probably also triggered only with -O1, do you want me to update all > 4 or just the new case? They're definitely not limited to -O1 (or weren't when added in 2015, commit dc6b5aed1b406a53c4512d355376b4e12c7da971). So it's only the new case for which a comment about being limited to -O1 is appropriate.
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..14655b77da 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. */ +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)
* 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(+)