This repository contains a small benchmark of the speed at which GCC, Clang, and MSVC handle _Generic expressions in C at various optimization settings.
The test file uses the preprocessor to generate 100,000 _Generic expressions, each supporting 24 types paired with empty functions:
_Generic( foo,
unsigned char: handle_unsigned_char,
signed char: handle_signed_char,
unsigned short: handle_unsigned_short,
short: handle_short,
unsigned int: handle_unsigned_int,
int: handle_int,
unsigned long: handle_unsigned_long,
long: handle_long,
unsigned long long: handle_unsigned_long_long,
long long: handle_long_long,
float: handle_float,
double: handle_double,
unsigned char *: handle_unsigned_char_ptr,
signed char *: handle_signed_char_ptr,
unsigned short *: handle_unsigned_short_ptr,
short *: handle_short_ptr,
unsigned int *: handle_unsigned_int_ptr,
int *: handle_int_ptr,
unsigned long *: handle_unsigned_long_ptr,
long *: handle_long_ptr,
unsigned long long *: handle_unsigned_long_long_ptr,
long long *: handle_long_long_ptr,
float *: handle_float_ptr,
double *: handle_double_ptr
)( foo )Each compiler is run five times, and the fastest compilation time is printed to the terminal.
To run the benchmark on Windows, execute ./run_bench.ps1 gcc clang cl from PowerShell.
To run the benchmark on Linux, execute bash run_bench.sh gcc clang.
Leave out a specific compiler by omitting the corresponding argument.
Results on Windows with an AMD Ryzen 7 5800H using MSVC 19.43.34810 and GCC 14.2.0 and Clang 19.1.7 via MinGW-w64:
