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commit d42269d7c85308abdbf8cee38b1a1097249eb38b appropriated the stream error flag temporarily to let the printf family of functions suppress further output attempts after encountering a write error. since the wide printf code relies on (narrow) vfprintf to print padding and numeric conversions, a hack was put in vfprintf not to clear the initial error status unless the stream is narrow oriented. this was okay, because calling vfprintf on a wide-oriented stream (outside of internal use by the implementation) produces undefined behavior. however, it was highly non-obvious to anyone reading the wide printf code, where the calls to fprintf without first checking for error status appeared erroneous. this patch removes all direct use of fprintf from the wide printf core, except in the numeric conversions case where it was already checked before starting processing of the directive that the error status is not set. the other calls, which were performing padding, are replaced by a new pad() helper function, which performs the check and abstracts out the mechanism of writing the padding. direct use of the error flag is also replaced by ferror, which is defined as a macro in stdio_impl.h, expanding directly to the flag check with no call or locking overhead.
musl libc
musl, pronounced like the word "mussel", is an MIT-licensed
implementation of the standard C library targetting the Linux syscall
API, suitable for use in a wide range of deployment environments. musl
offers efficient static and dynamic linking support, lightweight code
and low runtime overhead, strong fail-safe guarantees under correct
usage, and correctness in the sense of standards conformance and
safety. musl is built on the principle that these goals are best
achieved through simple code that is easy to understand and maintain.
The 1.1 release series for musl features coverage for all interfaces
defined in ISO C99 and POSIX 2008 base, along with a number of
non-standardized interfaces for compatibility with Linux, BSD, and
glibc functionality.
For basic installation instructions, see the included INSTALL file.
Information on full musl-targeted compiler toolchains, system
bootstrapping, and Linux distributions built on musl can be found on
the project website:
http://www.musl-libc.org/