A Hidden Weakness

a year ago

Android platform defines different API levels, with some symbols only available starting from certain API versions.
Using symbols like ASystemFontIterator_open on older APIs requires dynamic lookup via dlopen and dlsym or refusing to run on older APIs.
Android offers __ANDROID_UNAVAILABLE_SYMBOLS_ARE_WEAK__ for weak symbol definitions, combined with compiler and runtime checks.
Clang's -Werror=unguarded-availability ensures static checks for API level mismatches, preventing unsafe weak symbol calls.
Firefox's build system defaults to hidden visibility, causing weak symbols to be undefined in shared libraries, leading to crashes.
The fix involves temporarily changing visibility to default when including Android system headers to ensure symbols are correctly resolved.

Hasty Briefsbeta