Question

Is there a sequence point between structure member initialization expressions?

For example, is it well defined that the code bellow will always print “a, b”?

#include <stdio.h>

typedef struct {
    char *bytes;
    int position;
    int length;
} Stream;

typedef struct {
    char a;
    char b;
} Pair;

char streamgetc(Stream *stream) {
    return (stream->position < stream->length) ? stream->bytes[stream->position++] : 0;
}

int main(void) {
    Stream stream = {.bytes = "abc", .position = 0, .length = 3};
    Pair pair = {.a = streamgetc(&stream), .b = streamgetc(&stream)};
    printf("%c, %c\n", pair.a, pair.b);
    return 0;
}

Answer 1

I think §6.7.8-23 settles it:

The order in which any side effects occur among the initialization list
expressions is unspecified.

And about compound literals:

§6.5.2.5-7

All the semantic rules and constraints for initializer lists in 6.7.8
are applicable to compound literals.