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Re: cpp/icpp name clashes [BUG] [message #25839 is a reply to message #25805]

Mon, 15 March 2010 03:57

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Messages: 301
Registered: November 2008

Senior Member

Question:
How GCC, MSC, OW, CLANG compilers will assemble following source code consisted of FileName, FileName.cpp, FileName.h, FileName.icpp, main.cpp files?
Answer:
GCC input:

gcc -x c++ FileName FileName.cpp FileName.icpp main.cpp

GCC output files:

a.exe

MSC input:

cl /nologo /TP FileName FileName.cpp FileName.icpp main.cpp

MSC output:

FileName
FileName.cpp
FileName.icpp
main.cpp
Generating Code...
FileName.obj : warning LNK4042: object specified more than once; extras ignored
FileName.obj : warning LNK4042: object specified more than once; extras ignored
main.obj : error LNK2019: unresolved external symbol "int __cdecl ICppFunction(void)" (?ICppFunction@@YAHXZ) referenced in function _main
main.obj : error LNK2019: unresolved external symbol "int __cdecl CppFunction(void)" (?CppFunction@@YAHXZ) referenced in function _main
FileName.exe : fatal error LNK1120: 2 unresolved externals

OW input:

wcl386 -zq -cc++ FileName FileName.cpp FileName.icpp main.cpp

Some OW output:

Error! E2028: int near Function() is an undefined reference
Error! E2028: int near ICppFunction() is an undefined reference
file MAIN.obj(C:\MAIN.CPP): undefined symbol int near Function()
file MAIN.obj(C:\MAIN.CPP): undefined symbol int near ICppFunction()
Error: Linker returned a bad status

CLANG input:

clang -x c++ FileName FileName.cpp FileName.icpp main.cpp

CLANG output files:

a.out

Conclusion:
Some compilers can resolve extension clashes internally, but others only with output renaming.

Notes:
For testing used following tools:
gcc (TDM-2 mingw32) 4.4.1
Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 15.00.30729.01 for 80x86
Open Watcom C/C++32 Compile and Link Utility Version 1.9beta1 LA
clang version 1.1 (trunk 98527)

Source code:
File FileName:

#include "FileName.h"

int Function()
{
	return 0;
}

File FileName.cpp:

#include "FileName.h"

int CppFunction()
{
	return 1;
}

File FileName.h:

#ifndef __FileName_h__
#define __FileName_h__

int Function();
int CppFunction();
int ICppFunction();

#endif

File FileName.icpp:

#include "FileName.h"

int ICppFunction()
{
	return 2;
}

File main.cpp:

#include "FileName.h"

int main()
{
	int result = Function() + CppFunction() + ICppFunction();

	return result; // 3
}

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