Segmentation Fault before faulty code is ever reached?

**grumpy** · 01-11-2009

Boy, it's amazing the lengths people go to to defend their statements. Even more so, when those statements are all partially right and partially incorrect.

Originally Posted by cyberfish

Just get over it... a segfault is a UNIX/Linux/BSD thing, and GDB is the debugger that has >99% userbase on those systems.

You forget there are several commercial variants of unix (solaris, irix, MacOS/Darwin, etc) where gdb is not the default debugger.

Originally Posted by cyberfish

It's like saying we can't assume a person saying he is using IE 7 is on Windows.

As a matter of fact, you can't assume that. There are windows emulators that run under other operating systems.

Originally Posted by Elysia

Segmentation fault is a technical term, and believe or not, it also exists on Windows.

Yes, it does. However, when a forum post asks for help with code that generates a segmentation fault, it is a fair bet the poster is working under some variant of Unix. I would agree (see above) that does not justify an assumption they can/will use gdb.

Segmentation faults, when they occur under windows, are usually reported as a STATUS_ACCESS_VIOLATION exception (in either an error message, or within a popup dialog). There is no reference in that error message to the term "segmentation fault".

**cyberfish** · 01-11-2009

You forget there are several commercial variants of unix (solaris, irix, MacOS/Darwin, etc) where gdb is not the default debugger.

That's why I said 99%. Mac I think uses gdb/gcc, too, and I think Linux + Mac + BSD makes up 99% of *nix machines.

As a matter of fact, you can't assume that. There are windows emulators that run under other operating systems.

That's exactly the point. It's between politically correct and practically correct. How many people (in terms of % of IE users) runs IE under wine anyways?

**yougene** · 01-11-2009

Wow, well this has been informative.

Thanks for all the input. Using gdb was useful. Does anyone know of a good starting point for learning gdb?

Should I be learning any other tools at this stage?

**bboozzoo** · 01-12-2009

https://www.cs.colostate.edu/wiki/Gdb here's a decent bunch of references to number of tutorials

**laserlight** · 01-12-2009

Originally Posted by yougene

Does anyone know of a good starting point for learning gdb?

I "cheat" by using Code::Blocks as a front end.

**Maz** · 01-12-2009

Yes. Learning valgrind is usefull. It is really good with finding spots where memory is incorrectly used.

And with gdb you can get started with following basic commands:

start it

gdb <exename>

<run program>
type run <exe parameters if there is such>

To interrupt, hit ctrl+c

<getting backtrace from stack>
type bt

going "up" and "down" at stack calls, use
frame <number shown in backtrace>

To see local variables, type
info locals

to get a value of variable type
inspect <var name>

to continue executing program, type
c

To kill program being debugged, type
kill

If app is threaded, type
info threads

To switch to another threads context, type
thread <number>

to set a breakpoint, type
bp <function name, or file:line>

And finally, to dig deeper,
type help

I wrote these out of my head, so some mistakes may be present.

EDIT: Another lightweight frontend to gdb is ddd. Some also use eclipse as IDE, and it supports gdb too - also remote debugging (with gdbserver).

Me? I like things simple. gdb as it is, and vim is enough as an "IDE" for me

**yougene** · 01-12-2009

Thanks for all the suggestions I'll look through them and get on it.

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