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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. On most systems (anything with a flat memory hierarchy rather than using segment-based addressing), size_t and uintptr_t are the same type. However, on CHERI, size_t is just an integer offset, whereas uintptr_t is still a capability as described above. Casting a pointer to size_t will strip the metadata and validity tag, and casting from size_t to a pointer will result in a null-derived capability whose validity tag is not set, and thus cannot be dereferenced without faulting. The audio and cursor casts were harmless as they intend to stuff an integer into a pointer, but using uintptr_t is the idiomatic way to do that and silences our compiler warnings (which our build tool makes fatal by default as they often indicate real problems). The iconv and egl casts were true positives as SDL_iconv_t and iconv_t are pointer types, as is NativeDisplayType on most OSes, so this would have trapped at run time when using the round-tripped pointers. The gles2 casts were also harmless; the OpenGL API defines this argument to be a pointer type (and uses the argument name "pointer"), but it in fact represents an integer offset, so like audio and cursor the additional idiomatic cast is needed to silence the warning. |
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| .. | ||
| atomic | ||
| audio | ||
| core | ||
| cpuinfo | ||
| dynapi | ||
| events | ||
| file | ||
| filesystem | ||
| haptic | ||
| hidapi | ||
| joystick | ||
| libm | ||
| loadso | ||
| locale | ||
| main | ||
| misc | ||
| power | ||
| render | ||
| sensor | ||
| stdlib | ||
| test | ||
| thread | ||
| timer | ||
| video | ||
| SDL.c | ||
| SDL_assert.c | ||
| SDL_assert_c.h | ||
| SDL_dataqueue.c | ||
| SDL_dataqueue.h | ||
| SDL_error.c | ||
| SDL_error_c.h | ||
| SDL_hints.c | ||
| SDL_hints_c.h | ||
| SDL_internal.h | ||
| SDL_log.c | ||