Compiler error: memset was not declared in this scope

105
votes

I am trying to compile my C program in Ubuntu 9.10 (gcc 4.4.1).

I am getting this error:

Rect.cpp:344: error: ‘memset’ was not declared in this scope

But the problem is I have already included in my cpp file:

#include <stdio.h>
#include <stdlib.h>

And the same program compiles fine under Ubuntu 8.04 (gcc 4.2.4).

Please tell me what am I missing.

2
c++gcc
Something I still don't understand is why it compiles fine on older versions of gcc & ubuntu and not on newer versions. Can anyone explain why? – Dennis
@Dennis: probably because the necessary header <string.h> is being #included indirectly via some other #included header in your older gcc/Ubuntu configuration. – Paul R
@Dennis Adding -fpermissive to the gcc options might also help in those weird cases, although it is just a workaround – emu

2 Answers

183
votes

You should include <string.h> (or its C++ equivalent, <cstring>).

140
votes

Whevever you get a problem like this just go to the man page for the function in question and it will tell you what header you are missing, e.g.

$ man memset

MEMSET(3)                BSD Library Functions Manual                MEMSET(3)

NAME
     memset -- fill a byte string with a byte value

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <string.h>

     void *
     memset(void *b, int c, size_t len);

Note that for C++ it's generally preferable to use the proper equivalent C++ headers, <cstring>/<cstdio>/<cstdlib>/etc, rather than C's <string.h>/<stdio.h>/<stdlib.h>/etc.