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
ret
.Ltmp0:
...
str:
.asciz "Hi"
.size str, 3
...
[snip]
==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
Memcheck:Leak
fun:malloc
obj:/lib/libc.so.7
obj:/lib/libc.so.7
obj:/lib/libc.so.7
fun:puts
fun:main
}
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!
:-)
--
David Demelier
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