Re: C++ name mangling in C

[Marc Glisse <marc.glisse@inria.fr>]

On Sat, 9 Aug 2014, daniel@poradnik-webmastera.com wrote:

> Hi,
> C language does not use name mangling like C++. This can lead to subtle bugs, 
> when function prototype is declared differently in different files. Simple 
> example:
>
> /* file1.c */
> int test(int x, int y)
> {
>   return y;
> }
>
> /* file2.c */
> #include <stdio.h>
>
> extern int test(int x);
>
> int main()
> {
>   int n = test(2);
>   printf("n = %d\n", n);
>   return 0;
> }
>
> When this code is compiled using C++ compiler, such error will be reported at 
> linking phase as "undefined reference to 'test(int)'". Unfortunately in C 
> compilation and linking will succeed, so bug will appear at runtime. But such 
> bugs may be very hard to find.
>
> My code base is too big to clean up all this mess and move declarations to 
> header files manually in relatively short time. Therefore I was looking for a 
> way to detect such bugs with some tool. I thought about forcing C++ mangling 
> when compiling C code, but looks that gcc does not have any command line 
> option to this. Please correct me if I am wrong.
>
> If there is no such option, I would like to open an enhancement to add it. I 
> thought about it for some time and looks that this new option should do 3 
> things: enable C++ name mangling, enable extern "C" directive and define the 
> __cplusplus macro. Any comments on this proposal is also welcome.

How about compiling your code with g++ then? (possibly add -fpermissive to 
accept more C-isms)

If you define __cplusplus, you'll need a C++ compiler anyway because the 
headers will contain C++ code.

Compiling with -flto may also generate interesting messages.

-- 
Marc Glisse