undefined-reference

I have a function declared like so: template <typename T> T read(); and defined like so: template <typename T> T packetreader::read() { offset += sizeof(T); return *(T*)(buf+offset-sizeof(T)); } However, when I try to use it in my main() function: packetreader reader; reader.read<int>(); I get the following error from g++: g++ -o main main.o packet.o main.o: In function `main': main.cpp:(.text+0xcc): undefined reference to `int packetreader::read<int>()' collect2: ld returned 1 exit status make: *** [main] Error 1 Can anyone point me into the right direction? strager You need to use the export

Can't seem to get the errors to go away. Errors are below. I have looked on google and still can't figure it out. It is not like I am new to Cpp, but have not fooled with it in a while. Weird thing is it worked with G++ in Windows... Errors: [ze@fed0r! - - -** _ _*]$ g++ main.cpp /tmp/ccJL2ZHE.o: In function `main': main.cpp:(.text+0x11): undefined reference to `Help::Help()' main.cpp:(.text+0x1d): undefined reference to `Help::sayName()' main.cpp:(.text+0x2e): undefined reference to `Help::~Help()' main.cpp:(.text+0x46): undefined reference to `Help::~Help()' collect2: ld returned 1 exit

I have this simple code: max = (int) sqrt (number); and in the header I have: #include <math.h> But application still says undefined reference to sqrt . Do you see any problem here? It looks like everything should be okay. You may find that you have to link with the math libraries on whatever system you're using, something like: gcc -o myprog myprog.c -L/path/to/libs -lm ^^^ - this bit here. Including headers lets a compiler know about function declarations but it does not necessarily automatically link to the code required to perform that function. Failing that, you'll need to show us your

This question already has an answer here: undefined reference to sqrt (or other mathematical functions) 5 answers I have the following code (stripped down to the bare basics for this question): #include<stdio.h> #include<math.h> double f1(double x) { double res = sin(x); return 0; } /* The main function */ int main(void) { return 0; } When compiling it with gcc test.c I get the following error, and I can't work out why: /tmp/ccOF5bis.o: In function `f1': test2.c:(.text+0x13): undefined reference to `sin' collect2: ld returned 1 exit status However, I've written various test programs that call