Error while trying to use structs in C ++
I am trying to figure out how to use structs like lists in C ++. I came up with a piece of code that, for my understanding, shouldn't lead to any errors, but it happened ..
My code:
struct item {
int data;
struct item *next;
};
struct item *begin = NULL;
void add(int x) {
struct item *a = new struct item();
a->data = x;
a->next = begin;
begin = a;
}
int main() {
add(2);
printf("%d\n", begin->data);
return 0;
}
and this gives me the following:
Undefined symbols for architecture x86_64:
"operator new(unsigned long)", referenced from:
add(int) in structtest-f49486.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
I am using GCC inside my mac terminal to run my code. I haven't seen this before. I found that there is no error when I delete the line
struct item *a = new struct item();
Can anyone tell me what is wrong here?
Thank,
Merijn
source to share
Use g++
not gcc
. It looks like it is trying to link your C ++ code as C code.
GCC is so weird. When you use g++
to link it, it silently adds C ++ support libraries such as the one that defines the default operator new
.
And yes, he "forgets" that he just compiled the code as C ++. Don't ask me why.
Regarding clang
and gcc
, here's what I see on my Mac:
$ gcc --version
gcc (MacPorts gcc48 4.8.4_0) 4.8.4
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ type -a gcc
gcc is /opt/local/bin/gcc
gcc is /usr/bin/gcc
$ /usr/bin/gcc --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 6.1.0 (clang-602.0.49) (based on LLVM 3.6.0svn)
Target: x86_64-apple-darwin14.3.0
Thread model: posix
$ ls -lF /usr/bin/gcc
-rwxr-xr-x 1 root wheel 14160 Sep 29 2014 /usr/bin/gcc*
$ ls -lF /usr/bin/g++
-rwxr-xr-x 1 root wheel 14160 Sep 29 2014 /usr/bin/g++*
$ file /usr/bin/gcc
/usr/bin/gcc: Mach-O 64-bit executable x86_64
$ file /usr/bin/g++
/usr/bin/g++: Mach-O 64-bit executable x86_64
$ diff /usr/bin/g++ /usr/bin/gcc
Binary files /usr/bin/g++ and /usr/bin/gcc differ
Note that I have MacPorts installed, with real GCC 4.8 installed and configured to "replace" Apple "gcc". BTW, Apple is gcc
not a symbolic link.
source to share