It must have been. The version in the PellesC headers is pretty opaque:

````c
/* macros */
#define setjmp(env)  _setjmp3((env),0)

/* type definitions */
typedef int jmp_buf[16];

/* declarations */
extern int __cdecl _setjmp3(jmp_buf, int);  /* MS compatible */
extern _CRTEND void __cdecl longjmp(jmp_buf, int);
````

I assumed that the ``MS compatible`` there meant I could just assume it was the same struct layout, I guess.