Re: [PATCH v7 2/2] tty: add rpmsg driver

[Arnaud POULIQUEN]

On 3/26/20 1:01 AM, Joe Perches wrote:
> On Wed, 2020-03-25 at 14:31 +0100, Jiri Slaby wrote:
>> The question was exactly about that: can a compiler optimize it to a
>> bare number or will strlen call remain there?
> 
> $ cat str.c
> #include <string.h>
> 
> int foo(void)
> {
> 	return strlen("abc");
> }
> 
> $ gcc -c -O2 str.c
> $ objdump -d str.o
> str.o:     file format elf64-x86-64
> 
> 
> Disassembly of section .text:
> 
> 0000000000000000 <foo>:
>    0:	f3 0f 1e fa          	endbr64 
>    4:	b8 03 00 00 00       	mov    $0x3,%eax
>    9:	c3                   	retq   
> 
> 
same result with  arm gcc using  -O1 or -Og:

str.o:     file format elf32-littlearm


Disassembly of section .text:

00000000 <foo>:
   0:	e3a00003 	mov	r0, #3
   4:	e12fff1e 	bx	lr

So in conclusion replacing sizeof by srlen even if not optimized in -o0, right?

Thanks,
Arnaud