Editing Nm (Unix) (section)

==nm output sample==

<syntaxhighlight lang="c">
/*
 * File name: test.c
 * For C code compile with: 
 * gcc -c test.c
 *
 * For C++ code compile with:
 * g++ -c test.cpp
 */

int global_var;
int global_var_init = 26;

static int static_var;
static int static_var_init = 25;

static int static_function()
{
	return 0;
}

int global_function(int p)
{
	static int local_static_var;
	static int local_static_var_init=5;

	local_static_var = p;

	return local_static_var_init + local_static_var;
}

int global_function2()
{
	int x;
	int y;
	return x+y;
}

#ifdef __cplusplus
extern "C"
#endif
void non_mangled_function()
{
	// I do nothing
}

int main(void)
{
	global_var = 1;
	static_var = 2;

	return 0;
}

</syntaxhighlight>

If the previous code is compiled with the [[GNU Compiler Collection|gcc]] C compiler, the output of the <code>nm</code> command is the following:

<syntaxhighlight lang="console">
# nm test.o
0000000a T global_function
00000025 T global_function2
00000004 C global_var
00000000 D global_var_init
00000004 b local_static_var.1255
00000008 d local_static_var_init.1256
0000003b T main
00000036 T non_mangled_function
00000000 t static_function
00000000 b static_var
00000004 d static_var_init
</syntaxhighlight>

When the C++ compiler is used, the output differs:
<syntaxhighlight lang="console">
# nm test.o
0000000a T _Z15global_functioni
00000025 T _Z16global_function2v
00000004 b _ZL10static_var
00000000 t _ZL15static_functionv
00000004 d _ZL15static_var_init
00000008 b _ZZ15global_functioniE16local_static_var
00000008 d _ZZ15global_functioniE21local_static_var_init
         U __gxx_personality_v0
00000000 B global_var
00000000 D global_var_init
0000003b T main
00000036 T non_mangled_function
</syntaxhighlight>

The differences between the outputs also show an example of solving the [[name mangling]] problem by using [[extern "C"]] in C++ code.
{| class="wikitable"
  |+ Symbol types
|-
  ! Symbol type
  ! Description
|-
  | A 
  |Global absolute symbol
|-
  | a 
  | Local absolute symbol
|-
  | B 
  | Global bss symbol
|-
  | b 
  | Local bss symbol
|-
  | D 
  | Global data symbol
|-
  | d 
  | Local data symbol
|-
  | f 
  | Source file name symbol
|-
  | R
  | Global read-only symbol
|-
  | r
  | Local read-only symbol
|-
  | T
  | Global text symbol
|-
  | t
  | Local text symbol
|-
  | U
  | Undefined symbol
|}