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Eclipse Mixing C and C++ [message #1720182]

Thu, 14 January 2016 18:23

Eclipse User

I'm using Eclipse Europa with the TS-7800 embedded linux board.

I know Europa is an old release of Eclipse, but I'd prefer to use it for now.

Projects work if they are all C or all C++, but when mixing C in a C++ project, the C file is not included at link time so errors result.
The same would be the result with a C++ file not being linked in a C project.

I'd like to continue with my development and fix this for now. Later I can switch to another Eclipse version with my linux board if that works better.

Thanks,

Coleman

Re: Eclipse Mixing C and C++ [message #1720262 is a reply to message #1720182]

Fri, 15 January 2016 10:40

Eclipse User

A few questions

Which version of CDT are you using?
What is your host OS (Windows, Linux, etc)?
How do you build your project? Do use your own Makefiles?
Which toolchain are you using?
Can you paste the build output (Console view)?

I doubt you will get much help with such an old version of Eclipse (8 years old?). This is probably an issue that has been fixed.
I gave this a quick try; I added a test.c file to an existing C++ project and it was linked:
g++ -o "testHello" ./src/Base.o ./src/Child.o ./src/test.o ./src/testHello.o

This is using the CDT master branch (CDT 9.0)

Re: Eclipse Mixing C and C++ [message #1720263 is a reply to message #1720182]

Fri, 15 January 2016 10:44

Eclipse User

Did you surround the prototypes for the C code such as below?

// link to a C function
extern "C" {
void PrintHello();
}

If you don't, the linker will be looking for a mangled name despite reporting an error using the unmangled one.

EDIT:

I removed the extraneous ';' after the extern statement.
To further comment, here's the linker output without the extern "C":

Invoking: GCC C++ Linker
g++  -o "GSL_TEST"  ./src/GSL_TEST.o ./src/PrintHello.o   -lgsl -lgslcblas -lm
./src/GSL_TEST.o: In function `main':
/home/dvavra/workspaces/workspace/GSL_TEST/Debug/../src/GSL_TEST.cpp:22: undefined reference to `PrintHello()'
collect2: error: ld returned 1 exit status

Note that PrintHello.o is being linked but the linker says it can't find PrintHello() despite it being contained in PrintHello.c. Is this similar to what you are seeing?

[Updated on: Fri, 15 January 2016 11:00] by Moderator

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