402_variadic_functions.c File Reference

Unit test for FFI calls to and from variadic C functions. More...

#include "common/double_tap.h"
#include "common/infix_config.h"
#include "types.h"
#include <infix/infix.h>
#include <math.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>

Include dependency graph for 402_variadic_functions.c:

Macros
#define	DBLTAP_IMPLEMENTATION

Functions
int	forward_variadic_checker (char *buffer, size_t size, const char *format,...)
int	forward_variadic_aggregate_checker (int fixed_arg,...)
int	variadic_reverse_handler (const char *topic,...)
	subtest ("Forward variadic call")
	subtest ("Forward variadic call (aggregates)")
	subtest ("Reverse variadic callback")
	subtest ("Platform ABI: macOS AArch64 variadic struct passing")
	subtest ("Platform ABI: Windows x64 variadic float/double passing")

Variables
	TEST

Detailed Description

Unit test for FFI calls to and from variadic C functions.

This test file is extremely important for verifying ABI-compliance, as the rules for passing variadic arguments differ significantly between platforms, even on the same architecture.

The test covers:

• Forward Variadic Call (Primitives): A call is made to a printf-like function with a mix of fixed and variadic arguments (*char, int, double). This tests the core variadic calling mechanism.
• Forward Variadic Call (Aggregates): A call is made passing a struct as a variadic argument. This is highly platform-dependent:
  • On System V, the struct is passed on the stack.
  • On Windows x64, a pointer to the struct is passed in a GPR.
  • On AArch64, the struct is passed on the stack.
• Reverse Variadic Callback: A reverse trampoline is created for a variadic function. The test verifies that when the JIT-compiled function pointer is called with variadic arguments, the C handler receives them correctly via va_list/va_arg.
• Platform-Specific ABI Deviations: Includes dedicated subtests for known tricky variadic cases, such as passing floats/doubles on Windows x64 (which requires them to be passed in both GPRs and XMM registers) and passing structs on macOS on ARM (which has its own unique stack-passing rules).

Macro Definition Documentation

DBLTAP_IMPLEMENTATION

#define DBLTAP_IMPLEMENTATION

Function Documentation

forward_variadic_aggregate_checker()

int forward_variadic_aggregate_checker	(	int	fixed_arg,
			...
	)

forward_variadic_checker()

int forward_variadic_checker	(	char *	buffer,
		size_t	size,
		const char *	format,
			...
	)

subtest() [1/5]

subtest

(

"Forward variadic call (aggregates)"

)

subtest() [2/5]

subtest

(

"Forward variadic call"

)

subtest() [3/5]

subtest

(

"Platform ABI: macOS AArch64 variadic struct passing"

)

subtest() [4/5]

subtest

(

"Platform ABI: Windows x64 variadic float/double passing"

)

subtest() [5/5]

subtest

(

"Reverse variadic callback"

)

variadic_reverse_handler()

int variadic_reverse_handler	(	const char *	topic,
			...
	)

Variable Documentation

TEST

TEST

Initial value:

{
    plan(5)