The HP compiler on HP-UX 11.11 warns:

 Warning (anachronism) 823: ".../test_INT_format.h", line 194 # Redundant
 preprocessing concatenation operation results in two valid preprocessing
 tokens. Depending on this implementation defined behavior will result in
 non-portable code.
       TEST_C(INT32_C, -0x55000000, i32, int32_t, uint32_t)
       ^^^^^^
 Warning (anachronism) 823: ".../test_INT_format.h", line 196 # Redundant
 preprocessing concatenation operation results in two valid preprocessing
 tokens. Depending on this implementation defined behavior will result in
 non-portable code.
       TEST_C(INT64_C, -0x5500000000000000, i64, int64_t, uint64_t)
       ^^^^^^

There is likely a subtle problem with the way one of the system-provided type
macros is defined but the test passes despite the warning.  Simply suppress it.