5.10.1 Specific Compiler Characteristics

Some compilers exhibit different behaviors.

Static/Dynamic Expressions

Autoconf relies on a trick to extract one bit of information from the C compiler: using negative array sizes. For instance the following excerpt of a C source demonstrates how to test whether `int's are 4 bytes long:

int main (void) { static int test_array [sizeof (int) == 4 ? 1 : -1]; test_array [0] = 0 return 0; }

To our knowledge, there is a single compiler that does not support this trick: the HP C compilers (the real one, not only the "bundled") on HP-UX 11.00:

$ cc -c -Ae +O2 +Onolimit conftest.c cc: "conftest.c": error 1879: Variable-length arrays cannot \ have static storage.

Autoconf works around this problem by casting sizeof (int) to long before comparing it.