From 73fed37c046414206935ad1c5351fc0103f953b3 Mon Sep 17 00:00:00 2001 From: "Ryan C. Gordon" Date: Mon, 13 Jul 2026 18:30:53 -0400 Subject: [PATCH] assert: make disabled asserts work with bitfield conditions. We don't care _what_ the `sizeof` results are, we just want it to vaporize the condition's code out of the build. So we check it with a `? 1 : 0`, so it always boils down to a `sizeof (int)`, no matter what data type the condition actually is. This works with bitfields, pointers, anything that can be "truthy." If it isn't truthy, it would fail when assertions are enabled anyhow. Fixes #15990. (manually cherry picked from commit daf519ae05802c525344f058338ccc6596481813) --- include/SDL_assert.h | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/include/SDL_assert.h b/include/SDL_assert.h index 3a8446234d..a3d102538d 100644 --- a/include/SDL_assert.h +++ b/include/SDL_assert.h @@ -84,11 +84,16 @@ assert can have unique static variables associated with it. #define SDL_LINE __LINE__ /* -sizeof (x) makes the compiler still parse the expression even without -assertions enabled, so the code is always checked at compile time, but +sizeof ((x) ? 1 : 0) makes the compiler still parse the expression even +without assertions enabled, so the code is always checked at compile time, but doesn't actually generate code for it, so there are no side effects or -expensive checks at run time, just the constant size of what x WOULD be, +expensive checks at run time, just the constant size of what int would be, which presumably gets optimized out as unused. + +(The `? 1 : 0` is so this always dithers down to `sizeof (int)`...otherwise +you'll have problems when bitfields are used as the condition, since the +compiler will error out on the sizeof.) + This also solves the problem of... int somevalue = blah(); @@ -107,7 +112,7 @@ disable assertions. #endif #define SDL_disabled_assert(condition) \ - do { (void) sizeof ((condition)); } while (SDL_NULL_WHILE_LOOP_CONDITION) + do { (void) sizeof ((condition) ? 1 : 0); } while (SDL_NULL_WHILE_LOOP_CONDITION) typedef enum {