[SOLVED] Dealing with static functions when building a program as a library

Andy Alt · 12-15-2018, 02:50 PM

To implement unit testing, I've added a rule to build my program as a static library when "make check" is run. I wrap main() with #ifndef TEST_LIB and #endif (TEST_LIB is defined when it's built as a library).

Then I created some small C files to test some functions from that library.

Some of the functions from the library are declared statically.

Which you may guess produces warnings such as this when I try to compile the tests:

Code:

/../test/config_test.c:15:3: warning: implicit declaration of function ‘realize_home’ [-Wimplicit-function-declaration]

Because realize_home is declared statically in the source code (a .c file) for the program.

One solution I tried was to #include config_rmw (which contains the static functions) into the .c unit file (config_test). That actually works and doesn't give me any warnings when I compile, even though config_rmw.c is already built into the library.

Another solution I thought of was something like

Code:

#ifndef TEST_LIB
static
#endif
void function()
{
  definition
}

And adding the prototype to the header, which an #ifdef statement.

Code:

#ifdef TEST_LIB
function prototype
#endif

But doing that doesn't feel quite right, especially when it would have to be done for more functions as I proceed with implementing more unit tests.

I read in a book recently that static functions should go into a header file. I tried that but it only partially solved my problem. I wound up with compiler warnings like:

Code:

In file included from ../../src/rmw.c:38:0:
../../src/config_rmw.h:86:1: warning: ‘realize_home’ defined but not used [-Wunused-function]
 realize_home (char **str)
 ^~~~~~~~~~~~

I did some reading and I kind of understand why that happens. And basically that means I'd get a separate copy of that function in each .c file that #includes the header file where it's defined. Which I don't need. The reason I declare some functions statically is because they're only needed in one file.

Then I read some comments where people said static functions should never be defined in header files!

So... I'm stuck with wondering about the best approach and other options. I prefer to keep my programs organized and practice good coding skills.

I wrote some tests using just a script-based approach, which doesn't require my program to be built as a library, but I think there would be advantages to using both methods, depending on the functions that are being tested.

NevemTeve · 12-17-2018, 02:25 AM

Try something like this:

Code:

/* foobar_test.c */

#include "foobar.c"

int main (void)
{
    do tests here
}

pan64 · 12-17-2018, 05:02 AM

Quote:

Originally Posted by Andy Alt

Code:

/../test/config_test.c:15:3: warning: implicit declaration of function ‘realize_home’ [-Wimplicit-function-declaration]

Because realize_home is declared statically in the source code (a .c file) for the program.

No, that is not the reason. implicit function declaration means the compiler found a call to that function before the declaration itself.

https://stackoverflow.com/questions/...ternal-linkage

Andy Alt · 12-17-2018, 11:56 AM

Quote:

Originally Posted by pan64

No, that is not the reason. implicit function declaration means the compiler found a call to that function before the declaration itself.

https://stackoverflow.com/questions/...ternal-linkage

That's the usual reason, but in this case the warning is being caused by the static declaration. I'm calling the function from config_test.c but it's defined statically in config_rmw.c. That warning never shows when I build the program for non-testing.

Quote:

Originally Posted by NevemTeve

Try something like this:

Code:

/* foobar_test.c */

#include "foobar.c"

int main (void)
{
    do tests here
}

That's the method I've been using the last few days. And maybe I should just be happy with that since it's just set up that way for tests. I've been trained not to include .c files in other .c files so I wanted to investigate other options.

pan64 · 12-17-2018, 12:16 PM

what you wish is (at least I think) against the rule of the language. static means it is local to that c file, so cannot be reached from outside.
you may try to add test functions:

Code:

static void realize_home(char **)
{
    implementation
}
#ifdef UNITTEST
void test_realize_home(char **v)
{
    realize_home(v);
}
#endif

NevemTeve · 12-17-2018, 12:25 PM

> I've been trained not to include .c files in other .c files so I wanted to investigate other options.

Yes, but that rule is for normal usages. This case is a special usage.