Catch2 Sections as Macros

Question

I like from the C++ unit test framework Catch2 its sections -- much more than the xUnit test fixtures. Therefore I wrote me some macros which mimic the Catch2 sections.

This is the first macro heavy code I wrote, so I am mostly interested whether the macros do what they should do, or not.

#include <utility>
#define TOKENPASTE_HELPER(x, y) x ## y
#define TOKENPASTE(x, y) TOKENPASTE_HELPER(x, y)
#define CASE( name ) \
 if ( int executed_section = 0, first_run = 0; true ) \
 while ( std::exchange(executed_section, 0) || first_run++ == 0 )
#define SECTION( name ) \
 static int TOKENPASTE(counter_done_, __LINE__) = 0; \
 goto TOKENPASTE(section_start_, __LINE__); \
 TOKENPASTE(section_end_, __LINE__): \
 continue; \
 TOKENPASTE(section_start_, __LINE__): \
 while ( true ) \
 if ( TOKENPASTE(counter_done_, __LINE__) == 2 ) { \
 break; \
 } else if( TOKENPASTE(counter_done_, __LINE__) == 1 ) { \
 TOKENPASTE(counter_done_, __LINE__) = 2; \
 goto TOKENPASTE(section_end_, __LINE__); \
 } else if ( TOKENPASTE(counter_done_, __LINE__) = 1, executed_section=1; true )

They are used like this:

#include <cassert>
int main() {
 CASE( i_test ) {
 int i = 0;
 SECTION( i==1 ) {
 ++i;
 assert( i == 1 );
 }
 SECTION( i == 0 ) {
 assert( i == 0 );
 }
 }
 CASE( ii_test ) {
 int i = 10;
 SECTION() {
 assert( i==10 );
 }
 }
}

• Reinderien: Just... sigh. Don't use macros. But since you are using macros, please show the output of gcc -E or equivalent.

Answer 1

The output of gcc -E is

int main() {
 if ( int executed_section = 0, first_run = 0; true ) while ( std::exchange(executed_section, 0) || first_run++ == 0 ) {
 int i = 0;
 static int counter_done_27 = 0; goto section_start_27; section_end_27: continue; section_start_27: while ( true ) if ( counter_done_27 == 2 ) { break; } else if( counter_done_27 == 1 ) { counter_done_27 = 2; goto section_end_27; } else if ( counter_done_27 = 1, executed_section=1; true ) {
 ++i;
 assert( i == 1 );
 }
 static int counter_done_32 = 0; goto section_start_32; section_end_32: continue; section_start_32: while ( true ) if ( counter_done_32 == 2 ) { break; } else if( counter_done_32 == 1 ) { counter_done_32 = 2; goto section_end_32; } else if ( counter_done_32 = 1, executed_section=1; true ) {
 assert( i == 0 );
 }
 }
 if ( int executed_section = 0, first_run = 0; true ) while ( std::exchange(executed_section, 0) || first_run++ == 0 ) {
 int i = 10;
 static int counter_done_39 = 0; goto section_start_39; section_end_39: continue; section_start_39: while ( true ) if ( counter_done_39 == 2 ) { break; } else if( counter_done_39 == 1 ) { counter_done_39 = 2; goto section_end_39; } else if ( counter_done_39 = 1, executed_section=1; true ) {
 assert( i==10 );
 }
 }
}

I do recommend that you check output like this for macro-heavy code. And... what does it even do. It feels like it's written to be a puzzle, and test frameworks shouldn't be a puzzle. The goto, exchange, non-re-entrant statics... None of this should see the light of day, and it should all be deleted. I strongly recommend that you retry this project and pretend that the precompiler does not exist. The same features can be implemented with contemporary C++, especially lambdas.

• tommsch: Well, the output of gcc -E is exactly what it should be.
• G. Sliepen: While I agree it would be better to write a test framework that doesn't require macros, if the goal is to make a drop-in replacement for Catch2, I don't see how you could do that.