demelier.david at gmail.com
Tue Mar 29 08:08:37 UTC 2011
On 29/03/2011 09:59, Eitan Adler wrote:
> Hi David,
>> It seems printf() always alloc something and does not free it:
> What compiler and what optimizations? Most compilers will optimize a
> printf without any special formatting into a puts call instead of a
> printf call.
I was using clang / gcc without any optimisations.
> For example clang -O3 -fomit-frame-pointer (which I use for clarity
> here) outputs this code:
> .file "leak.c"
> main: # @main
> # BB#0: # %entry
> subl $12, %esp
> movl $str, (%esp)
> calll puts
> xorl %eax, %eax
> addl $12, %esp
> .asciz "Hi"
> .size str, 3
>> ==67840== suppressed: 4,096 bytes in 1 blocks
> Lets take a look at what valgrind says immediately after this:
> ==14481== For counts of detected and suppressed errors, rerun with: -v
> One of the lines we get is
> --14508-- used_suppression: 1 libc puts leak
I didn't see this one, thanks!
> Which means it is a known issue and has been specially marked as to
> avoid being reported by valgrind.
> Lets take a look to see where this suppression happens: in
> /usr/local/lib/valgrind/default.supp we find
> libc puts leak
> After some investigation I was able to find the following commit:
> http://p4db.freebsd.org/chv.cgi?CH=168767 which shows when this
> suppression was added and by whom.
> I trust that if you are interested in the details of why this leak is
> detected you have the skills to follow up on this by yourself :-)
Thanks a lot for the details.
> Thank you for trying to make FreeBSD better!
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