Support DTrace in Mac

[vchuravy]

The implementation can be found hidden away in this header file https://opensource.apple.com/source/xnu/xnu-4570.41.2/osfmk/mach/i386/sdt_isa.h.auto.html

[vchuravy]

I am actually not sure how these get triggered...

Below is a generated header file provided from @NHDaly

Here the probes are just defined as call to __dtrace_probe$julia$compile_end$v1$63686172202a but that is marked as extern... because whos responsibility is to generate DTRACE_CALL0ARGS.
It might be feasible that we don't have to do the shared-library trick on Mac since they don't seem to use ELF notes or something similar than requires the usage of the linker.

/*
 * Generated by dtrace(1M).
 */

#ifndef	_UPROBES_H_GEN
#define	_UPROBES_H_GEN

#include <unistd.h>

#ifdef	__cplusplus
extern "C" {
#endif

#define JULIA_STABILITY "___dtrace_stability$julia$v1$1_1_0_1_1_0_1_1_0_1_1_0_1_1_0"

#define JULIA_TYPEDEFS "___dtrace_typedefs$julia$v2"

#if !defined(DTRACE_PROBES_DISABLED) || !DTRACE_PROBES_DISABLED

#define	JULIA_COMPILE_END(arg0) \
do { \
	__asm__ volatile(".reference " JULIA_TYPEDEFS); \
	__dtrace_probe$julia$compile__end$v1$63686172202a(arg0); \
	__asm__ volatile(".reference " JULIA_STABILITY); \
} while (0)
#define	JULIA_COMPILE_END_ENABLED() \
	({ int _r = __dtrace_isenabled$julia$compile__end$v1(); \
		__asm__ volatile(""); \
		_r; })
#define	JULIA_COMPILE_START() \
do { \
	__asm__ volatile(".reference " JULIA_TYPEDEFS); \
	__dtrace_probe$julia$compile__start$v1(); \
	__asm__ volatile(".reference " JULIA_STABILITY); \
} while (0)
#define	JULIA_COMPILE_START_ENABLED() \
	({ int _r = __dtrace_isenabled$julia$compile__start$v1(); \
		__asm__ volatile(""); \
		_r; })


extern void __dtrace_probe$julia$compile__end$v1$63686172202a(const char *);
extern int __dtrace_isenabled$julia$compile__end$v1(void);
extern void __dtrace_probe$julia$compile__start$v1(void);
extern int __dtrace_isenabled$julia$compile__start$v1(void);

#else

#define	JULIA_COMPILE_END(arg0) \
do { \
	} while (0)
#define	JULIA_COMPILE_END_ENABLED() (0)
#define	JULIA_COMPILE_START() \
do { \
	} while (0)
#define	JULIA_COMPILE_START_ENABLED() (0)

#endif /* !defined(DTRACE_PROBES_DISABLED) || !DTRACE_PROBES_DISABLED */


#ifdef	__cplusplus
}
#endif

#endif	/* _UPROBES_H_GEN */

[vchuravy]

Ok they are implemented very differently on Mac than on Linux https://opensource.apple.com/source/xnu/xnu-2050.9.2/bsd/dev/dtrace/dtrace.c

libusdt is a good blueprint: https://github.com/chrisa/libusdt