gcc -Wall warnings

[alexcohn]

When Android NDK compiles char_ref.c with -DNDEBUG -Wall, we see warnings:

char_ref.rl: In function 'consume_named_ref':
char_ref.rl:2498:12: warning: unused variable 'matched' [-Wunused-variable]
char_ref.rl:2512:12: warning: unused variable 'matched' [-Wunused-variable]

More warnings are triggered by -Wall -Wextra:

utf8.c:88:1: warning: 'static' is not at beginning of declaration [-Wold-style-declaration]
 uint32_t static inline decode(uint32_t* state, uint32_t* codep, uint32_t byte) {
 ^
utf8.c:88:1: warning: 'inline' is not at beginning of declaration [-Wold-style-declaration]

Another set of warnings (49) is triggered by -Wunused-variable, which is turned on by default with Clang -Wextra, e.g.:

error.c: In function 'find_next_newline':
error.c:150:17: warning: unused parameter 'original_text' [-Wunused-parameter]

Possible workarounds:

These unused-variable warnings could be addressed by #348, but the pull request has not been merged yet.

With GCC toolchain, I can hide all these warnings with LOCAL_CFLAGS=-Wno-unused-variable -Wno-unused-parameter -Wno-old-style-declaration for the gumbo-parser library, but not for Clang, which has been declared the only supported compiler in NDK 14.

The best fix for unused-variable and unused-parameter would be to add __attribute__ ((unused)) in relevant positions in source code.

Regarding utf8.c, the fix is simply to shuffle the keywords:

static inline uint32_t decode(uint32_t* state, uint32_t* codep, uint32_t byte) {