erik@powell:/tmp$ cat test.c

#include <math.h>

#include <stdio.h>

#include <string.h>

 

int main ()

{

  double (*fnct)(double);

 

  double i;

  char buf[19];

  scanf ("%p %lf %s", &fnct, &i, buf);

  printf ("%lf %d\n",fnct(i), strlen(buf));

  return 0;

}

erik@powell:/tmp$ gcc -lgsl -lm  -lgslcblas test.c -o test -g

erik@powell:/tmp$ gdb test

GNU gdb 6.8-debian

Copyright (C) 2008 Free Software Foundation, Inc.

License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software: you are free to change and redistribute it.

There is NO WARRANTY, to the extent permitted by law.  Type "show copying"

and "show warranty" for details.

This GDB was configured as "x86_64-linux-gnu"...

(gdb) b main

Breakpoint 1 at 0x4006a5: file test.c, line 11.

(gdb) r

Starting program: /tmp/test

 

Breakpoint 1, main () at test.c:11

11        scanf ("%p %lf %s", &fnct, &i, buf);

(gdb) p sqrt

$1 = {<text variable, no debug info>} 0x7fa6075f3d50 <sqrt>

(gdb) p sqrt(4)

$2 = 0

(gdb) set variable fnct=sqrt

(gdb) set variable i=4

(gdb) p fnct(i)

$3 = 2

erik@powell:/tmp$ gcc -v -lgsl -lm  -lgslcblas test.c -o test -g

Using built-in specs.

Target: x86_64-linux-gnu

Configured with: ../src/configure -v --with-pkgversion='Debian 4.3.2-1.1' --with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.3 --program-suffix=-4.3 --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-mpfr --enable-cld --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu

Thread model: posix

gcc version 4.3.2 (Debian 4.3.2-1.1)

COLLECT_GCC_OPTIONS='-v' '-o' 'test' '-g' '-mtune=generic'

 /usr/lib/gcc/x86_64-linux-gnu/4.3.2/cc1 -quiet -v test.c -quiet -dumpbase test.c -mtune=generic -auxbase test -g -version -o /tmp/ccChhzYk.s

ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"

ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/4.3.2/../../../../x86_64-linux-gnu/include"

ignoring nonexistent directory "/usr/include/x86_64-linux-gnu"

#include "..." search starts here:

#include <...> search starts here:

 /usr/local/include

 /usr/lib/gcc/x86_64-linux-gnu/4.3.2/include

 /usr/lib/gcc/x86_64-linux-gnu/4.3.2/include-fixed

 /usr/include

End of search list.

GNU C (Debian 4.3.2-1.1) version 4.3.2 (x86_64-linux-gnu)

        compiled by GNU C version 4.3.2, GMP version 4.2.2, MPFR version 2.3.2.

warning: MPFR header version 2.3.2 differs from library version 2.3.1.

GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072

Compiler executable checksum: 3741a6052d20b6389f93b1cc4a619780

COLLECT_GCC_OPTIONS='-v' '-o' 'test' '-g' '-mtune=generic'

 as -V -Qy -o /tmp/cca0LLSw.o /tmp/ccChhzYk.s

GNU assembler version 2.18.0 (x86_64-linux-gnu) using BFD version (GNU Binutils for Debian) 2.18.0.20080103

COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.3.2/:/usr/lib/gcc/x86_64-linux-gnu/4.3.2/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.3.2/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.3.2/:/usr/lib/gcc/x86_64-linux-gnu/

LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.3.2/:/usr/lib/gcc/x86_64-linux-gnu/4.3.2/:/usr/lib/gcc/x86_64-linux-gnu/4.3.2/../../../../lib/:/lib/../lib/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/4.3.2/../../../:/lib/:/usr/lib/

COLLECT_GCC_OPTIONS='-v' '-o' 'test' '-g' '-mtune=generic'

 /usr/lib/gcc/x86_64-linux-gnu/4.3.2/collect2 --eh-frame-hdr -m elf_x86_64 --hash-style=both -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o test /usr/lib/gcc/x86_64-linux-gnu/4.3.2/../../../../lib/crt1.o /usr/lib/gcc/x86_64-linux-gnu/4.3.2/../../../../lib/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.3.2/crtbegin.o -L/usr/lib/gcc/x86_64-linux-gnu/4.3.2 -L/usr/lib/gcc/x86_64-linux-gnu/4.3.2 -L/usr/lib/gcc/x86_64-linux-gnu/4.3.2/../../../../lib -L/lib/../lib -L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/4.3.2/../../.. -lgsl -lm -lgslcblas /tmp/cca0LLSw.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/x86_64-linux-gnu/4.3.2/crtend.o /usr/lib/gcc/x86_64-linux-gnu/4.3.2/../../../../lib/crtn.o