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Old 11-22-2011, 12:52 AM   #1
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A serious problem when migrating C programs from Aix to Linux (gcc)

We used to write sprintf(*str, "%03s", *v_str) to output string with '0' left padded to length of 3. This worked fine on Aix, but on Linux gcc (4.1.2), it left pads with space instead. This causes us big trouble as we don't know which programs to check. We have hundreds of programs that may have this!
Is there a 'global' way, say a compiler option, a global modifier etc that can change this behavior?
Old 11-22-2011, 05:05 AM   #2
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No, there is no easy way to change this behaviour, which is to do with the library rather than the compiler. This particular usage of leading zero padding with the string format is explicitly undefined in the ANSI standard, so the code is non-portable.

A work-around might be something like:
int width = 3;
sprintf(str, "%.*d%s", width-strlen(v_str), 0, v_str);
You can use grep '%0[0-9]*s' to search your source files for format strings with this problem.

Last edited by neonsignal; 11-22-2011 at 06:07 AM. Reason: added grep suggestion
Old 11-22-2011, 05:47 AM   #3
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ooops... posted something stupid without proper reading. Deleted.


Last edited by jlinkels; 11-22-2011 at 05:48 AM.
Old 11-22-2011, 06:25 AM   #4
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Thank you. It will be a pain for us to search...


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