How to get a backtrace from a C module

How to get a backtrace from a C module

[biju64]

Hello,

I am trying to generate a backtrace into a file of the stack when a program
errors. I can see the gcc functions backtrace_symbols and backtrace. But
when I add it to a small C program and build I cannot find the execinfo.h
file and the two relevant functions. The progarm I use is reproduced below
(from the example):



#include 
#include 
#include 

/* Obtain a backtrace and print it to stdout. */
void
print_trace (void)
{
  void *array[10];
  size_t size;
  char **strings;
  size_t i;

  size = backtrace (array, 10);
  strings = backtrace_symbols (array, size);

  printf ("Obtained %zd stack frames.\n", size);

  for (i = 0; i < size; i++)
     printf ("%s\n", strings[i]);

  free (strings);
}

/* A dummy function to make the backtrace more interesting. */
void
dummy_function (void)
{
  print_trace ();
}

int
main (void)
{
  dummy_function ();
  return 0;
}




My version is:

gcc -v  
Reading specs from /usr/sfw/lib/gcc/sparc-sun-solaris2.10/3.4.3/specs
Configured with:
/gates/sfw10/builds/sfw10-gate/usr/src/cmd/gcc/gcc-3.4.3/configure
--prefix=/usr/sfw --with-as=/usr/sfw/bin/gas --with-gnu-as
--with-ld=/usr/ccs/bin/ld --without-gnu-ld --enable-languages=c,c++
--enable-shared
Thread model: posix
gcc version 3.4.3 (csl-sol210-3_4-branch+sol_rpath)


Please help if you can...I just need to get a stack dump similar to the one
you see when analysing a core file using gdb.
Cheers,
Alex
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Re: How to get a backtrace from a C module

[John Love-Jensen]

Hi Alex,

Isn't backtrace and backtrace_symbols part of the GNU C Library?

q.v. http://www.delorie.com/gnu/docs/glibc/libc_665.html

Are you using the GNU C Library, or the Sun C Library?

--Eljay

Re: How to get a backtrace from a C module

[biju64]

John Love-Jensen wrote:
> 
> Hi Alex,
> 
> Isn't backtrace and backtrace_symbols part of the GNU C Library?
> 
> q.v. http://www.delorie.com/gnu/docs/glibc/libc_665.html
> 
> Are you using the GNU C Library, or the Sun C Library?
> 
> --Eljay
> 

Hi Eljay,
Thanks for the reply. I thought so too...that's where I discovered the
example etc.
I am using the GNU C library (I think)...When I do a ldd on an executable
thus created I see the following:

        ....
        librt.so.1 =>    /usr/lib/librt.so.1
        libm.so.2 =>     /usr/lib/libm.so.2
        libsocket.so.1 =>        /usr/lib/libsocket.so.1
        libz.so.1 =>     /usr/lib/libz.so.1
        libnsl.so.1 =>   /usr/lib/libnsl.so.1
        libpthread.so.1 =>       /usr/lib/libpthread.so.1
        libc.so.1 =>     /usr/lib/libc.so.1        libaio.so.1 =>  
/usr/lib/libaio.so.1
        libmd5.so.1 =>   /usr/lib/libmd5.so.1
        libgcc_s.so.1 =>         /usr/sfw/lib/libgcc_s.so.1
        libmp.so.2 =>    /usr/lib/libmp.so.2
        libscf.so.1 =>   /usr/lib/libscf.so.1
        libdoor.so.1 =>  /usr/lib/libdoor.so.1
        libuutil.so.1 =>         /usr/lib/libuutil.so.1
        /platform/SUNW,Sun-Blade-2500/lib/libc_psr.so.1
        /platform/SUNW,Sun-Blade-2500/lib/libmd5_psr.so.1

As libgcc_s.so.1 is in the path I would assume it is.  But the compiler
can't find the execinfo.h file either that describes the prototype for these
functions let alone the functions themselves. Please help...

Alex
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Re: How to get a backtrace from a C module

[John Love-Jensen]

Hi Alex,

As I understand it, libgcc_s.so.1 is not the GNU C Library, rather it is the
GCC Support library, containing things like soft float, abort, pow,
trampoline support, stack unwinding, malloc/calloc/free, strlen, and perhaps
other stuff (depending on platform).

Keep in mind that the GNU C Library (glibc) is a separate project from GNU
Compiler Collection (GCC).

--Eljay

Re: How to get a backtrace from a C module

[biju64]

Thank you very much all for the replies.
I can see the 'error' of my ways :-)
Will look further into this...



John Love-Jensen wrote:
> 
> Hi Alex,
> 
> As I understand it, libgcc_s.so.1 is not the GNU C Library, rather it is
> the
> GCC Support library, containing things like soft float, abort, pow,
> trampoline support, stack unwinding, malloc/calloc/free, strlen, and
> perhaps
> other stuff (depending on platform).
> 
> Keep in mind that the GNU C Library (glibc) is a separate project from GNU
> Compiler Collection (GCC).
> 
> --Eljay
> 
> 
> 

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Re: How to get a backtrace from a C module

[Brian Dessent]

biju64 wrote:

> I am using the GNU C library (I think)...When I do a ldd on an executable

No, you're not if you're on Solaris.  You're using Sun's C library.

>         libc.so.1 =>     /usr/lib/libc.so.1

This is the C library.  It is not part of gcc.

>         libgcc_s.so.1 =>         /usr/sfw/lib/libgcc_s.so.1

This is libgcc.  It is part of gcc, but it is only a small support
library containing things like multiplication routines for systems
without hardware floating point.

As Eljay already pointed out, the feature you're trying to use is part
of glibc, so there is no point trying to use it if you are not on a
GNU/Linux or GNU/Hurd system.  There may still be other ways to get a
backtrace, but you would have to consult the system documentation for
Solaris.

Brian