sscanf + c99 not working on some platforms ?

Question

When I compile a simple Hello World! program that uses the sscanf function on my local Debian lenny x64, it works. But when I upload the same program to the server running CentOS x86, it will not work. If I do not use sscanf, then the program works on both computers.

gcc -std=c99 -O2 -pipe -m32

If I compile it with sscanf but without -std=c99, then it works on both computers.

gcc -O2 -pipe -m32

What is the problem with sscanf and c99 on CentOS x86 ? I thought that compiling with the -m32 flag would work on all Linuxes ? (I have limited access to the CentOS server, so I do not have access to error messages.)

Answer 1

Are you uploading the binary or the source and then recompiling? If you are uploading the binary, you are probably running into a library compatibility issue between Debian and CentOS.

If that is the case, upload the source only and recompile on CentOS.

Answer 2

If you do not have permission to compile @ CentOS, then try compiling a static binary. You can use dietlibc which makes smaller binaries than glibc or try EGLIBC which is the default C library that Debian will use starting Debian "squeeze".

Answer 3

Probably the CentOS box is using an old version of glibc. Since the nonstandard GNU extensions to their scanf implementation ended up making glibc conflict with c99, they added a nasty hack of redirecting *scanf to __isoc99_*scanf when -std=c99 is in use; if your copy of glibc is missing the __isoc99_sscanf symbol, the program will then fail to run.

Static linking, or linking to a different libc without ugly backwardsness-compatibility hacks, would solve the problem.

Answer 4

Probably the CentOS box is using an old version of glibc. Since the nonstandard GNU extensions to their scanf implementation ended up making glibc conflict with c99, they added a nasty hack of redirecting *scanf to __isoc99_*scanf when -std=c99 is in use; if your copy of glibc is missing the __isoc99_sscanf symbol, the program will then fail to run.

Static linking, or linking to a different libc without ugly backwardsness-compatibility hacks, would solve the problem.