If you are including the .h file for the .c file in your .cpp file and it
doesn't already have extern "C" in it, wrapping it like this when including it
in your cpp should help:
extern "C"
{
#include "header.h"
}
Sent from my Verizon Wireless 4G LTE smartphone
-------- Original message --------
From: J Decker <[email protected]>
Date: 06/05/2015 10:33 PM (GMT-05:00)
To: Sunrise <[email protected]>
Cc: [email protected]
Subject: Re: [CMake] undefined reference to error when use "c" extension
c++ does name mangling on functions... so functions like 'f' become a much more
complex name (as shown in the xxx not found in your error messages).
In order for C++ to not produce a mangled name C functions have to be defined as
extern "c" void f( void );
but 'extern "c"' is not liked by C... so you really need to define in the
shared header something like...
#ifdef __cplusplus
#define CEXTERN extern "C"
#ese
#define CEXTERN
#endif
CEXTERN void f( void );
But of course since you don't know about name mangling I guess you don't know
proper header usage either. This is not a cmake issue, but a general C++
issue... and you'd do better asking stack exchange or something.
On Fri, Jun 5, 2015 at 6:37 PM, Sunrise
<[email protected]<mailto:[email protected]>> wrote:
Hello,
I am linking my code to a library. My code is in C++ but the library is in C.
The problem is that whenever the extension of library implementations are "c"
(not cpp), they are not linked and I get "undefined reference to" error.
Here is an example:
Suppose I have
./src/main.cpp // as main file
./include/lib.h
./include/lib.c // as a library
And the cmake file is
cmake_minimum_required(VERSION 2.8)
project(myproj)
set(INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/include)
include_directories(${INCLUDE_DIR})
add_library(MY_LIB ${INCLUDE_DIR}/Lib.c)
set(EXECUTABLE_NAME "myproj")
set(SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/src)
add_executable(myproj ${SOURCE_DIR}/main.cpp)
target_link_libraries(myproj MY_LIB)
This returns undefined reference to error, but if I rename lib.c to lib.cpp,
everything works fine.
How can I resolve this? I do not want to rename the file to cpp, because there
are a lot of library files and I prefer to keep the library implementations
untouched.
Thanks.
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