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Old 05-15-2012, 05:44 AM   #1
smilebhuff
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SIGSEGV segmentation fault at strftime_l lib64/libc.so.6


I'am porting pro*c codes from UNIX to LINUX. The codes are compiled and created executables successfully. But during run time its raising segmentation fault. I debugged the code step by step and the below is the output of GDB debug.

Breakpoint 4 at 0x3b19690f50 (gdb) n 525 strftime (buf, MAX_STRING_LEN, "%d/%b/%Y:%H:%M:%S", dummy_time); (gdb) n

Breakpoint 4, 0x0000003b19690f50 in strftime () from /lib64/libc.so.6 (gdb) n Single stepping until exit from function strftime, which has no line number information. 0x0000003b19690f70 in strftime_l () from /lib64/libc.so.6 (gdb) n Single stepping until exit from function strftime_l, which has no line number information.

Program received signal SIGSEGV, Segmentation fault. 0x0000003b19690f8b in strftime_l () from /lib64/libc.so.6

Actually in code the function strftime() is called not strftime_l(). But I have no idea why it is reaching strftime_l in /lib64/libc.so.6.

This issue is not coming in UNIX. please help on this.
 
Old 05-15-2012, 06:21 AM   #2
pan64
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I think it is pretty obvious, see man strftime. strftime has an implicite default locale, otherwise both do the same thing (so strftime calls strftime_l with an additional argument)
The segfault can be caused by either the buffer is too small or by an illegal variable handling (so for example dummy_time points to nowhere)
 
Old 05-15-2012, 07:13 AM   #3
smilebhuff
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thanks for you reply. From my application code strftime() is called. But the segmentation fault is at strftime_l() .

Program received signal SIGSEGV, Segmentation fault. 0x0000003b19690f8b in strftime_l () from /lib64/libc.so.6

My first question is why its going to strftime_l() when am calling strftime() in code.
 
Old 05-15-2012, 07:18 AM   #4
pan64
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because strftime does nothing else just calls strftime_l passing all the original arguments and an additional one: the locale settings. The functionality is implemented in the function strftime_l.
 
Old 05-15-2012, 07:22 AM   #5
smilebhuff
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could please help me where to see the definition or implementation of strftime() ? I tried to check whether it calls strftime_l() but I couldn't get where this function implementation is seen?
 
Old 05-15-2012, 07:46 AM   #6
pan64
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(this is obvious). It is usual in the linux world: you can have a few similar functions with almost the same functionality. some of them has default values or assumes some settings. In such cases all those functions invoke the most general one passing their inputs and adding the assumed ones. The functionality is implemented only once and in this general version.

Since this is part of libc you need to download the source code of it and look into the code for the real implementation (there will be a strftime.c or similar). you can find it for example here: http://www.gnu.org/software/libc/download.html
 
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Old 05-15-2012, 09:35 AM   #7
smilebhuff
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you are saying that strftime() calls strftime_l(). Is that on assumption or?
 
Old 05-15-2012, 09:44 AM   #8
pan64
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that is coming from your post. You told you wrote strftime, but you see strftime_l, and asked why. Either you called directly strftime_l or it is called from strftime. The "Single stepping until exit from function strftime" just walked into strftime_l and the code is died inside strftime_l.
 
Old 05-15-2012, 10:24 AM   #9
smilebhuff
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ok pan.. thanks for your instant replies.. modified code .. and it woked now!!
 
  


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