Any utility to test expand C/C++ #define macros?

Go to https://godbolt.org/. Enter your code in the left pane and select compiler as gcc put the argument as -E in the right pane. Your pre-processed code will appear on the right.

You can just run your code through the preprocessor, which will show you what it will be expanded into (or spit out errors as necessary):

$ cat a.c
#define GETADDR_FOR(a) if (!(a = (#_#a)GetProcAddress(h, "/""#a"/""))) 
GETADDR_FOR(hexdump)

$ gcc -E a.c
# 1 "a.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "a.c"
a.c:1:36: error: '#' is not followed by a macro parameter

GETADDR_FOR(hexdump)

In GCC, it's gcc -E foo.c to only preprocess the file.

Visual Studio uses the /P argument.

http://visualstudiogallery.msdn.microsoft.com/59a2438f-ba4a-4945-a407-a1a295598088 - visual studio plugin to expand macroses