musl libc – Catalog

musl is cataloged separately from glibc by design: same POSIX surface, very different implementation choices and extension set. The authoritative inventory is ledger-musl.md – 1482 functions across 110 public-header families of musl 1.2.5, extracted from the musl source tree (with the _Noreturn-aware fix: the BSD err/warn family and _Exit were initially missed by naive prototype parsing), plus computed deltas against the glibc inventory (musl-only: 15; glibc-only: ~2367).

In this section

• Family pages under musl/<family>.md document the families where musl’s behavior genuinely differs from glibc, each entry with musl source-file provenance (src/... paths), WHATSNEW version notes, and explicit unverified markers where no source was reachable.
• The glibc-side equivalents are cross-linked from the glibc function pages rather than duplicated.

Key verified deltas (evidence in family pages)

• Flat ABI: no symbol versioning, dlvsym meaningless; dynlink lookup ignores versions (musl ldso/dynlink.c).
• ucontext: all four functions declared in ucontext.h, no implementation anywhere in src/ – linking fails (sharper than the usual “no makecontext”).
• No execinfo.h/backtrace; no nsswitch, RES_OPTIONS, or LOCALDOMAIN handling; iconv uses a fixed built-in charset table; ctype _l variants ignore locale.
• getdents64 is a macro for getdents; LFS64 macros gated by _LARGEFILE64_SOURCE (1.2.4+).
• crypt in libc proper (glibc 2.41: libcrypt.so.1); mallocng allocator; setxid broadcast via __synccall.
• musl ignores POSIXLY_CORRECT in getopt; supports GNU long options, permutation, and optional args.