Re: Extraneous test in setsignal()?

Denys Vlasenko <[email protected]> wrote:
> void setsignal(int signo)
> {
> ...
>        if ((t = trap[signo]) == NULL)
>                action = S_DFL;
>        else if (*t != '\0')
>                action = S_CATCH;
>        else
>                action = S_IGN;
>        if (rootshell && action == S_DFL && !lvforked) {
> ...
> 
> If you read the above carefully, you see that action == S_DFL check
> can be eliminated if we rewrite the above like this:
> 
>        new_act = S_DFL;
>        if ((t = trap[signo]) != NULL)
>                new_act = S_CATCH;
>                if (t[0] == '\0')
>                        new_act = S_IGN;
>        } else if (rootshell && !lvforked) {
> ...
> 
> 

Thanks.  But that's exactly what gcc 14 generates anyway:

  b2:   44 8b 35 00 00 00 00    mov    0x0(%rip),%r14d        # b9 <setsignal+0x29>
                        b5: R_X86_64_PC32       vforked-0x4
        if ((t = trap[signo]) == NULL)
  b9:   48 85 c0                test   %rax,%rax
  bc:   0f 84 ee 00 00 00       je     1b0 <setsignal+0x120>

...

        if (rootshell && action == S_DFL && !lvforked) {
 1b0:   44 89 f0                mov    %r14d,%eax
 1b3:   0b 05 00 00 00 00       or     0x0(%rip),%eax        # 1b9 <setsignal+0x129>
                        1b5: R_X86_64_PC32      shlvl-0x4
 1b9:   75 1d                   jne    1d8 <setsignal+0x148>
                switch (signo) {
 1bb:   83 fa 16                cmp    $0x16,%edx
 1be:   77 18                   ja     1d8 <setsignal+0x148>

Cheers,
-- 
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
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