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Theta91

Member

Registered: 2014-08-21

Posts: 13

[SOLVED] [C] localtime() segfault solved by tzset() -- why?

status.c (sp. line 110): https://github.com/Theta91/dotfiles/blo … tus.c#L110
status.h: https://github.com/Theta91/dotfiles/blo … c/status.h
Makefile: https://github.com/Theta91/dotfiles/blo … c/Makefile

In order to pick back up some of my lost C skills, I decided to mess around with writing a small statusline program ala the various dwm status bars. Anyway, I came across a curiosity: running a for loop w/ fmt_date works fine - once, then it segfaults*. The trace** indicated a problem with getenv that I eventually solved by using setenv() + tzset(), but this doesn't seem to be a problem with any other dwm status bars I've seen, which use functionally identical code [that also caused a segfault for me], so: why is this?

[I did go back and check my /etc/localtime and all that -- it's correct]

*i.e.

/: 13.9G /home: 284.9G | 100 HOME-7B52 | F | Fri 29 Aug '14 00:12:53
zsh: segmentation fault  ./status

**trace:

#0  0x00007ffff775fead in getenv () from /usr/lib/libc.so.6
#1  0x00007ffff77d4988 in tzset_internal () from /usr/lib/libc.so.6
#2  0x00007ffff77d4d19 in __tz_convert () from /usr/lib/libc.so.6
#3  0x0000000000400e90 in fmt_date () at status.c:121
#4  0x0000000000400bff in main () at status.c:53

edit: It actually appears to disappear w/o tzset() when I actually allocate space for 'status' - perhaps that was the problem? *facepalm*

Last edited by Theta91 (2014-08-29 16:12:05)

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 19,797

Re: [SOLVED] [C] localtime() segfault solved by tzset() -- why?

edit: It actually appears to disappear w/o tzset() when I actually allocate space for 'status' - perhaps that was the problem? *facepalm*

If that was rhetorical, Go ahead and mark your thread as solved.
It was not rhetorical, yes, not having allocated space would do it.  Still mark the thread as solved

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