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Add and use SDL_FALLTHROUGH for fallthroughs

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Case fallthrough warnings can be suppressed using the __fallthrough__
compiler attribute. Unfortunately, not all compilers have this
attribute, or even have __has_attribute to check if they have the
__fallthrough__ attribute. [[fallthrough]] is also available in C++17
and the next C2x, but not everyone uses C++17 or C2x.

So define the SDL_FALLTHROUGH macro to deal with those problems - if we
are using C++17 or C2x, it expands to [[fallthrough]]; else if the
compiler has __has_attribute and has the __fallthrough__ attribute, then
it expands to __attribute__((__fallthrough__)); else it expands to an
empty statement, with a /* fallthrough */ comment (it's a do {} while
(0) statement, because users of this macro need to use a semicolon,
because [[fallthrough]] and __attribute__((__fallthrough__)) require a
semicolon).

Clang before Clang 10 and GCC before GCC 7 have problems with using
__attribute__ as a sole statement and warn about a "declaration not
declaring anything", so fall back to using the /* fallthrough */ comment
if we are using those older compiler versions.

Applications using SDL are also free to use this macro (because it is
defined in begin_code.h).

All existing /* fallthrough */ comments have been replaced with this
macro. Some of them were unnecessary because they were the last case in
a switch; using SDL_FALLTHROUGH in those cases would result in a compile
error on compilers that support __fallthrough__, for having a
__attribute__((__fallthrough__)) statement that didn't immediately
precede a case label.
This commit is contained in:
Misa
2021-09-27 14:38:12 -07:00
committed by Ozkan Sezer
parent c877dd93c5
commit 3bf7994fe2
15 changed files with 65 additions and 55 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
src/stdlib/SDL_iconv.c
View File

@@ -758,7 +758,7 @@ SDL_iconv(SDL_iconv_t cd,
if (ch > 0x10FFFF) {
ch = UNKNOWN_UNICODE;
}
/* fallthrough */
SDL_FALLTHROUGH;
case ENCODING_UCS4BE:
if (ch > 0x7FFFFFFF) {
ch = UNKNOWN_UNICODE;
@@ -780,7 +780,7 @@ SDL_iconv(SDL_iconv_t cd,
if (ch > 0x10FFFF) {
ch = UNKNOWN_UNICODE;
}
/* fallthrough */
SDL_FALLTHROUGH;
case ENCODING_UCS4LE:
if (ch > 0x7FFFFFFF) {
ch = UNKNOWN_UNICODE;

12
src/stdlib/SDL_string.c
View File

@@ -1275,7 +1275,7 @@ SDL_vsscanf(const char *text, const char *fmt, va_list ap)
}
}
}
/* Fall through to %d handling */
SDL_FALLTHROUGH;
case 'd':
if (inttype == DO_LONGLONG) {
Sint64 value;
@@ -1323,13 +1323,13 @@ SDL_vsscanf(const char *text, const char *fmt, va_list ap)
if (radix == 10) {
radix = 8;
}
/* Fall through to unsigned handling */
SDL_FALLTHROUGH;
case 'x':
case 'X':
if (radix == 10) {
radix = 16;
}
/* Fall through to unsigned handling */
SDL_FALLTHROUGH;
case 'u':
if (inttype == DO_LONGLONG) {
Uint64 value = 0;
@@ -1815,7 +1815,7 @@ SDL_vsnprintf(SDL_OUT_Z_CAP(maxlen) char *text, size_t maxlen, const char *fmt,
case 'p':
case 'x':
info.force_case = SDL_CASE_LOWER;
/* Fall through to 'X' handling */
SDL_FALLTHROUGH;
case 'X':
if (info.force_case == SDL_CASE_NOCHANGE) {
info.force_case = SDL_CASE_UPPER;
@@ -1826,12 +1826,12 @@ SDL_vsnprintf(SDL_OUT_Z_CAP(maxlen) char *text, size_t maxlen, const char *fmt,
if (*fmt == 'p') {
inttype = DO_LONG;
}
/* Fall through to unsigned handling */
SDL_FALLTHROUGH;
case 'o':
if (info.radix == 10) {
info.radix = 8;
}
/* Fall through to unsigned handling */
SDL_FALLTHROUGH;
case 'u':
info.force_sign = SDL_FALSE;
if (info.precision >= 0) {