Community
cancel
Showing results for 
Search instead for 
Did you mean: 
vkrevs
Beginner
127 Views

RTC failure on FD_ZERO in any program compiled with -debug -check-uninit on openSUSE 11.2 or Ubuntu 9.10

Hi. I was wondering if someone could help me with the following issue.

I've just installed Intel C++ compiler 11.1/059 on openSUSE 11.1 for x86_64. It appears that any program contaning the FD_ZERO macro with abort with an RTC failure if compiled in -debug -check-uninit mode. For example, put the following into a file called /tmp/foo.cpp:

#include
#include
#include
int main (int argc, char ** argv)
{
fd_set readfds;
FD_ZERO (&readfds);
return EXIT_SUCCESS;
}

Then compile it:
. /opt/intel/Compiler/11.1/059/bin/iccvars.sh intel64
icpc -debug -check-uninit -c -o foo.o foo.cpp
icpc -o foo foo.o.

Then run it and observe the crash:
$ /tmp/foo

Run-Time Check Failure: The variable '__d1' is being used without being initialized

Aborted


The '__d1' variable is used in the GLIBC's definition of the FD_ZERO macro in /usr/include/bits/select.h:
....
# if __WORDSIZE == 64
# define __FD_ZERO_STOS "stosq"
# define __FD_SET_BTS "btsq"
# define __FD_CLR_BTR "btrq"
# define __FD_ISSET_BT "btq"
# else
...
# endif

# define __FD_ZERO(fdsp) \
do {<><------><------><------><------><------><------><------><------> \
int __d0, __d1;<---><------><------><------><------><------><------> \
__asm__ __volatile__ ("cld; rep; " __FD_ZERO_STOS<-><------><------> \
<------><------><------> : "=c" (__d0), "=D" (__d1)<--><------><------> \
<------><------><------> : "a" (0), "0" (sizeof (fd_set)<-----><------> \
<------><------><------><------><------> / sizeof (__fd_mask)),<------> \
<------><------><------> "1" (&__FDS_BITS (fdsp)[0])><------><------> \
<------><------><------> : "memory");<><------><------><------><------> \
} while (0)


Any suggestions?

$ rpm -q gcc glibc
gcc-4.4-4.2.x86_64
glibc-2.10.1-10.4.x86_64
0 Kudos
5 Replies
TimP
Black Belt
127 Views

Why not initialize it yourself, at least while using -check? Try several values to assure yourself the operation of your application doesn't depend on initial values.
vkrevs
Beginner
127 Views

Quoting - tim18
Why not initialize it yourself, at least while using -check? Try several values to assure yourself the operation of your application doesn't depend on initial values.

Hmm, I thought I was making sure my cross-platform application does not depend on initial values by using FD_ZERO in this particular case. Isn't the whole point of FD_ZERO macro is to provide a standard way to initialize an fd_set?


vkrevs
Beginner
127 Views

Same issue on Ubuntu 9.10 for x86_64. Seems like a generic problem that will occur on any system with a modern glibc (>= 2.10.x).
Om_S_Intel
Employee
127 Views

I can reproduce this in FC11 as well.

The compiler behaviour is correct. If you do not use -check-uninit compiler option then the compiler does not check for the uninitialized variables and the compiled binary runs.

vkrevs
Beginner
127 Views

I can reproduce this in FC11 as well.

The compiler behaviour is correct. If you do not use -check-uninit compiler option then the compiler does not check for the uninitialized variables and the compiled binary runs.

Are you saying that there is a bug in FD_ZERO's implementation in glibc 2.10.x, that is FD_ZERO's implementation in glibc 2.10.x relies on unintialized data? Valgrind does not report it ... Just out of curiosity, do you intend to work with glibc maintainers to resolve this issue?
Reply