On Mon, Jun 27, 2011 at 5:45 PM, Mike Frysinger <[email protected]> wrote:
> On Friday, June 24, 2011 10:39:29 Jie Zhang wrote:
>> On Fri, Jun 17, 2011 at 4:39 PM, Mike Frysinger wrote:
>> > On Friday, June 17, 2011 16:09:47 Jie Zhang wrote:
>> >> On Fri, Jun 17, 2011 at 1:58 PM, Mike Frysinger wrote:
>> >> >> + const char *ex_short = "[firmware=FILE]";
>> >> >> + const char *ex_desc = "FILE Upgrade the ICE firmware. See
>> >> >> this
>> >> >
>> >> > page:\n"
>> >> >
>> >> > const char foo[] = "..."
>> >>
>> >> Why?
>> >
>> > one less pointer. compare the assembly output:
>> > $ echo 'const char foo[] = "asdf";' | gcc -S -o - -x c -
>> > $ echo 'const char *foo = "asdf";' | gcc -S -o - -x c -
>>
>> But when it's passed as an argument, the former will pass the whole
>> string but the latter will only pass a pointer.
>
> no it wont. in both cases, passing it as an argument will pass a pointer.
>
On x86_64-linux-gnu host with -O2, the former:
ice_cable_help:
.LFB70:
.cfi_startproc
subq $152, %rsp
.cfi_def_cfa_offset 160
movabsq $8242000105019369051, %rcx
movabsq $26253366783262053, %rdx
movq %rcx, 128(%rsp)
movq %rdx, 136(%rsp)
movl %edi, %eax
movq %rsi, %r8
movq %rsp, %rdi
movl $.LC3, %esi
movl $15, %ecx
rep movsq
movq %rsp, %rcx
movl (%rsi), %edx
movq %r8, %rsi
movl %edx, (%rdi)
movzwl .LC3+124(%rip), %edx
movw %dx, 4(%rdi)
leaq 128(%rsp), %rdx
movl %eax, %edi
call urj_tap_cable_generic_usbconn_help_ex
addq $152, %rsp
ret
.cfi_endproc
.LFE70:
.size ice_cable_help, .-ice_cable_help
The latter:
ice_cable_help:
.LFB70:
.cfi_startproc
movl $.LC3, %ecx
movl $.LC4, %edx
jmp urj_tap_cable_generic_usbconn_help_ex
.cfi_endproc
.LFE70:
.size ice_cable_help, .-ice_cable_help
Jie
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