Add a function to clamp a value to a range.
SDL_clamp(x, a, b) is equivalent to SDL_min(a, SDL_max(x, b)): it
ensures that x is not smaller than a, nor larger than b.
While, as best I can tell, this isn't actually standardised anywhere,
it's a very useful function/macro to have.
The __clang_major__ and __clang_minor__ macros provide a marketing
version, which is not necessarily comparable for clang distributions
from different vendors[1]. In practice, the versioning scheme for
Apple's clang is indeed completely different to that of the llvm.org
releases. It is thus preferable to check for features directly rather
than comparing versions.
In this specific case, __builtin_bswap16 was being used with older
Apple clang versions that don't support it.
[1] https://clang.llvm.org/docs/LanguageExtensions.html#builtin-macros
- cmake, configure (CheckDLOPEN): --enable-sdl-dlopen is now history..
detach the dl api discovery from SDL_LOADSO_DLOPEN functionality.
define HAVE_DLOPEN. also define DYNAPI_NEEDS_DLOPEN (CheckDLOPEN is
called only for relevant platforms.)
- update SDL_config.in and SDL_config.cmake accordingly.
- SDL_dynapi.h: set SDL_DYNAMIC_API to 0 if DYNAPI_NEEDS_DLOPEN is
defined, but HAVE_DLOPEN is not.
- pthread/SDL_systhread.c: conditionalize dl api use to HAVE_DLOPEN
- SDL_x11opengl.c, SDL_DirectFB_opengl.c, SDL_naclopengles.c: rely
on HAVE_DLOPEN, not SDL_LOADSO_DLOPEN.
- SDL_config_android.h, SDL_config_iphoneos.h, SDL_config_macosx.h,
SDL_config_pandora.h, and SDL_config_wiz.h: define HAVE_DLOPEN.
Closes: https://github.com/libsdl-org/SDL/pull/4351
This is needed to support CHERI, and thus Arm's experimental Morello
prototype, where pointers are implemented using unforgeable capabilities
that include bounds and permissions metadata to provide fine-grained
spatial and referential memory safety, as well as revocation by sweeping
memory to provide heap temporal memory safety.
The referential safety is enforced through the use of tagged memory, and
there is only a single tag bit per capability-sized word, meaning it is
impossible to store capabilities at unaligned locations, either getting
a trap on load/store or the validity tag being stripped when
round-tripepd through memory.
Since this is a new ABI for which SDL has never been compiled before, we
do not need to be concerned with this compatibility measure, so just
don't pack the struct for CHERI architectures.
This code is inherently rather dubious anyway; if MSVC and GCC disagree
on struct layout when targeting Windows then that is a bug in GCC, but
likely extends from the bogus #pragma pack directives for MSVC in
begin_code.h, which will force types to be *underaligned* (and is
attempting to work around something that is fundamentally a broken idea
to be doing). In particular 8-byte-aligned types will be underaligned to
4 bytes, but only on MSVC. Since that code is not used for GCC that is
probably the cause of the struct layout discrepancy, and there are
likely other instances of that throughout SDL. Moreover, the supposed
fix here is not in fact a fix, as now GCC will think SDL_AudioCVT is
only 1-byte-aligned but MSVC will think it's 4-byte or 8-byte-aligned,
meaning ABI incomatibility is introduced by this change. However,
removing it would break ABI compatibility for purely-GCC-compiled code
(as old binaries would see the struct as 1-byte-aligned and new binaries
would see the struct as 8-byte-aligned) so SDL is stuck with this until
it bumps its ABI.
This is needed to support CHERI, and thus Arm's experimental Morello
prototype, where pointers are implemented using unforgeable capabilities
that include bounds and permissions metadata to provide fine-grained
spatial and referential memory safety, as well as revocation by sweeping
memory to provide heap temporal memory safety.
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