summaryrefslogtreecommitdiff
path: root/src/include/stdio.h
AgeCommit message (Collapse)AuthorLines
2019-03-12make FILE a complete type for pre-C11 standard profilesRich Felker-0/+2
C11 removed the requirement that FILE be a complete type, which was deemed erroneous, as part of the changes introduced by N1439 regarding completeness of types (see footnote 6 for specific mention of FILE). however the current version of POSIX is still based on C99 and incorporates the old requirement that FILE be a complete type. expose an arbitrary, useless complete type definition because the actual object used to represent FILE streams cannot be public/ABI. thanks to commit 13d1afa46f8098df290008c681816c9eb89ffbdb, we now have a framework for suppressing the public complete-type definition of FILE when stdio.h is included internally, so that a different internal definition can be provided. this is perfectly well-defined, since the same struct tag can refer to different types in different translation units. it would be a problem if the implementation were accessing the application's FILE objects or vice versa, but either would be undefined behavior.
2018-10-18bypass indirection through pointer objects to access stdin/out/errRich Felker-0/+18
by ABI, the public stdin/out/err macros use extern pointer objects, and this is necessary to avoid copy relocations that would be expensive and make the size of the FILE structure part of the ABI. however, internally it makes sense to access the underlying FILE objects directly. this avoids both an indirection through the GOT to find the address of the stdin/out/err pointer objects (which can't be computed PC-relative because they may have been moved to the main program by copy relocations) and an indirection through the resulting pointer object. in most places this is just a minor optimization, but in the case of getchar and putchar (and the unlocked versions thereof), ipa constant propagation makes all accesses to members of stdin/out PC-relative or GOT-relative, possibly reducing register pressure as well.