mirror of https://github.com/acidanthera/audk.git
9222154ae7
gcc-8 (which is part of Fedora 28) enables the new warning "-Wrestrict" in "-Wall". This warning is documented in detail at <https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html>; the introduction says > Warn when an object referenced by a restrict-qualified parameter (or, in > C++, a __restrict-qualified parameter) is aliased by another argument, > or when copies between such objects overlap. It breaks the BaseTools build (in the Brotli compression library) with: > In function 'ProcessCommandsInternal', > inlined from 'ProcessCommands' at dec/decode.c:1828:10: > dec/decode.c:1781:9: error: 'memcpy' accessing between 17 and 2147483631 > bytes at offsets 16 and 16 overlaps between 17 and 2147483631 bytes at > offset 16 [-Werror=restrict] > memcpy(copy_dst + 16, copy_src + 16, (size_t)(i - 16)); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > In function 'ProcessCommandsInternal', > inlined from 'SafeProcessCommands' at dec/decode.c:1833:10: > dec/decode.c:1781:9: error: 'memcpy' accessing between 17 and 2147483631 > bytes at offsets 16 and 16 overlaps between 17 and 2147483631 bytes at > offset 16 [-Werror=restrict] > memcpy(copy_dst + 16, copy_src + 16, (size_t)(i - 16)); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Paolo Bonzini <pbonzini@redhat.com> analyzed the Brotli source in detail, and concluded that the warning is a false positive: > This seems safe to me, because it's preceded by: > > uint8_t* copy_dst = &s->ringbuffer[pos]; > uint8_t* copy_src = &s->ringbuffer[src_start]; > int dst_end = pos + i; > int src_end = src_start + i; > if (src_end > pos && dst_end > src_start) { > /* Regions intersect. */ > goto CommandPostWrapCopy; > } > > If [src_start, src_start + i) and [pos, pos + i) don't intersect, then > neither do [src_start + 16, src_start + i) and [pos + 16, pos + i). > > The if seems okay: > > (src_start + i > pos && pos + i > src_start) > > which can be rewritten to: > > (pos < src_start + i && src_start < pos + i) > > Then the numbers are in one of these two orders: > > pos <= src_start < pos + i <= src_start + i > src_start <= pos < src_start + i <= pos + i > > These two would be allowed by the "if", but they can only happen if pos > == src_start so they degenerate to the same two orders above: > > pos <= src_start < src_start + i <= pos + i > src_start <= pos < pos + i <= src_start + i > > So it is a false positive in GCC. Disable the warning for now. Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Cole Robinson <crobinso@redhat.com> Cc: Liming Gao <liming.gao@intel.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Yonghong Zhu <yonghong.zhu@intel.com> Reported-by: Cole Robinson <crobinso@redhat.com> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Laszlo Ersek <lersek@redhat.com> Reviewed-by: Liming Gao <liming.gao@intel.com> |
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