c - Seg fault with time and ctime, when porting from Linux to OSX -

i getting errors compiling code designed (i believe) linux on osx. have tracked down issue section of code:

timeval = time(null); char* timestring = ctime(&timeval); timestring[24]=' ';  fprintf(log, "[ %20s] ", timestring); 

is there reason why might case? have included <time.h>.

ctime using statically allocated buffer of size, first problem you're appending string without knowing size.

timestring[24]=' '; 

this might cause segfault on it's own if buffer 24 bytes. cause might if zero-termination happens @ index 24, made string unterminated, , fprintf continue reading until hits memory it's not allowed read, resulting in segfault.

use ctime_r preallocated buffer if want modify it, , make sure buffer large enough hold data, , zero-terminated after you're done it. if ctime_r isn't available, strncpy own buffer before modifying.

hth

edit

i'm not sure you're trying do, assuming code posted taken directly application, you're looking this:

timeval = time(null); char* timestring = ctime(&timeval);  fprintf(log, "[ %20s ] ", timestring); 

that is, pad time string. add space in formatting string instead of in time-string buffer.