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Re: [PATCH v4] fix warnings in sys/select.h fortification with -Wsign-conversion


On Sat, Jun 9, 2012 at 1:24 PM, Paul Eggert <eggert@cs.ucla.edu> wrote:

>> it has slightly more overhead
>
> Not for any modern compiler with normal optimization;
> they all turn (0 <= x && x < CONSTANT) into a single
> unsigned comparison, even if x is signed.

Mike opened BZ#14210 for this, and I commented there:

on Linux/x86_64, the code for __fdelt_chk is identical before/after the patch:

(gdb) disas __fdelt_chk
Dump of assembler code for function __fdelt_chk:
   0x00000000000fb910 <+0>:    cmp    $0x3ff,%rdi
   0x00000000000fb917 <+7>:    ja     0xfb921 <__fdelt_chk+17>
   0x00000000000fb919 <+9>:    mov    %rdi,%rax
   0x00000000000fb91c <+12>:    shr    $0x6,%rax
   0x00000000000fb920 <+16>:    retq
   0x00000000000fb921 <+17>:    push   %rax
   0x00000000000fb922 <+18>:    callq  0xf9a60 <__GI___chk_fail>
End of assembler dump.


Can I have an explicit approval to commit (latest version of) my patch?

Thanks,
-- 
Paul Pluzhnikov


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