I know my understanding of #include or how it is compiled is not correct otherwise the code I have would work. I'm confused on why my code needs #include in two locations in order to compile and run correctly.
My main cpp file armperfmon.cpp:
#include "armperfmon.h"
int main(int argc, char* argv[])
{
FILE* pOutFile = NULL;
PrintCounterOptions(pOutFile);
}
main header file armperfmon.h:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "counters.h"
void PrintCounterOptions(FILE* pFile);
second cpp containing function counters.cpp:
void PrintCounterOptions(FILE* pFile)
{
fprintf("print some stuff");
}
second header file for function counters.h
void PrintCounterOptions(FILE* pFile);
The error:
counters.cpp: error: 'FILE' was not declared in this scope
counters.cpp: error: 'pFile' was not declared in this scope
if I enter #include <stdio.h> in the function cpp file then the error goes away and the function compiles/executes as expected. I assumed that in the main.h file when it included <stdio.h> it would be available for use for subsequent FILE* definitions especially because it is included before counters.h is included. As I type this I'm also realizing the more correct include is <cstdio>. If someone could clarify what is wrong with my thought process it would be much appreciated.
It's hard to answer this exactly because you've stripped out all the specific details like filenames but, in brief, C++ source files are compiled independently before the results are linked together, and the "main header" is not seen at all while compiling the "second cpp": it's only the header for your "main cpp file". Indeed, the entire purpose of header files is to serve as a common location for declarations that shall then be #included into multiple translation units, which is what you need to do here by adding the necessary code to your "second header file".