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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

24
src/video/SDL_blit.h
View File

@@ -479,14 +479,14 @@ do { \
#define DUFFS_LOOP8(pixel_copy_increment, width) \
{ int n = (width+7)/8; \
switch (width & 7) { \
case 0: do { pixel_copy_increment; /* fallthrough */ \
case 7: pixel_copy_increment; /* fallthrough */ \
case 6: pixel_copy_increment; /* fallthrough */ \
case 5: pixel_copy_increment; /* fallthrough */ \
case 4: pixel_copy_increment; /* fallthrough */ \
case 3: pixel_copy_increment; /* fallthrough */ \
case 2: pixel_copy_increment; /* fallthrough */ \
case 1: pixel_copy_increment; /* fallthrough */ \
case 0: do { pixel_copy_increment; SDL_FALLTHROUGH; \
case 7: pixel_copy_increment; SDL_FALLTHROUGH; \
case 6: pixel_copy_increment; SDL_FALLTHROUGH; \
case 5: pixel_copy_increment; SDL_FALLTHROUGH; \
case 4: pixel_copy_increment; SDL_FALLTHROUGH; \
case 3: pixel_copy_increment; SDL_FALLTHROUGH; \
case 2: pixel_copy_increment; SDL_FALLTHROUGH; \
case 1: pixel_copy_increment; \
} while ( --n > 0 ); \
} \
}
@@ -495,10 +495,10 @@ do { \
#define DUFFS_LOOP4(pixel_copy_increment, width) \
{ int n = (width+3)/4; \
switch (width & 3) { \
case 0: do { pixel_copy_increment; /* fallthrough */ \
case 3: pixel_copy_increment; /* fallthrough */ \
case 2: pixel_copy_increment; /* fallthrough */ \
case 1: pixel_copy_increment; /* fallthrough */ \
case 0: do { pixel_copy_increment; SDL_FALLTHROUGH; \
case 3: pixel_copy_increment; SDL_FALLTHROUGH; \
case 2: pixel_copy_increment; SDL_FALLTHROUGH; \
case 1: pixel_copy_increment; \
} while (--n > 0); \
} \
}

12
src/video/SDL_fillrect.c
View File

@@ -145,13 +145,13 @@ SDL_FillRect1(Uint8 * pixels, int pitch, Uint32 color, int w, int h)
switch ((uintptr_t) p & 3) {
case 1:
*p++ = (Uint8) color;
--n; /* fallthrough */
--n; SDL_FALLTHROUGH;
case 2:
*p++ = (Uint8) color;
--n; /* fallthrough */
--n; SDL_FALLTHROUGH;
case 3:
*p++ = (Uint8) color;
--n; /* fallthrough */
--n;
}
SDL_memset4(p, color, (n >> 2));
}
@@ -159,11 +159,11 @@ SDL_FillRect1(Uint8 * pixels, int pitch, Uint32 color, int w, int h)
p += (n & ~3);
switch (n & 3) {
case 3:
*p++ = (Uint8) color; /* fallthrough */
*p++ = (Uint8) color; SDL_FALLTHROUGH;
case 2:
*p++ = (Uint8) color; /* fallthrough */
*p++ = (Uint8) color; SDL_FALLTHROUGH;
case 1:
*p++ = (Uint8) color; /* fallthrough */
*p++ = (Uint8) color;
}
}
pixels += pitch;

2
src/video/SDL_pixels.c
View File

@@ -333,7 +333,7 @@ SDL_MasksToPixelFormatEnum(int bpp, Uint32 Rmask, Uint32 Gmask, Uint32 Bmask,
if (Rmask == 0) {
return SDL_PIXELFORMAT_RGB555;
}
/* fallthrough */
SDL_FALLTHROUGH;
case 16:
if (Rmask == 0) {
return SDL_PIXELFORMAT_RGB565;

2
src/video/directfb/SDL_DirectFB_WM.c
View File

@@ -323,7 +323,7 @@ DirectFB_WM_ProcessEvent(_THIS, SDL_Window * window, DFBWindowEvent * evt)
}
if (window->flags & SDL_WINDOW_MAXIMIZED)
return 1;
/* fall through */
SDL_FALLTHROUGH;
default:
windata->wm_grab = pos;
if (grabbed_window != NULL)

2
src/video/directfb/SDL_DirectFB_events.c
View File

@@ -261,7 +261,7 @@ ProcessWindowEvent(_THIS, SDL_Window *sdlwin, DFBWindowEvent * evt)
SDL_SendWindowEvent(sdlwin, SDL_WINDOWEVENT_MOVED,
evt->x, evt->y);
}
/* fall throught */
SDL_FALLTHROUGH;
case DWET_SIZE:
/* FIXME: what about < 0 */
evt->w -= (windata->theme.right_size + windata->theme.left_size);

1
src/video/windows/SDL_windowsevents.c
View File

@@ -729,6 +729,7 @@ WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
}
}
/* don't break here, fall through to check the wParam like the button presses */
SDL_FALLTHROUGH;
case WM_LBUTTONUP:
case WM_RBUTTONUP:
case WM_MBUTTONUP: