Libc

« libc » ou « bibliothèque standard C ».

Sommaire

GNU libc
- Auteur initial : Roland McGrath
- Mainteneur : le dictateur Ulrich Drepper
- Licence GNU LGPL
- Bugzilla
- Documentation : The GNU C Library manual
- Lire son code source en ligne (git)
Bionic
- Bionic is the standard C library (including libc, libdl, libm, and libpthread) developed by Google for its Android operating system.
uClibc
- Ne nécessite pas de MMU
- Écrite pour fonctionner sur un microcontrôleur
- Écrite depuis zéro, mais inclut du code la GNU libc et autres projets
- Licence GNU LGPL
EGLIBC
- Variante de la GNU libc destinée à l'embarqué
dietlibc
- Écrite depuis zéro
- Vise clairement l'embarqué : libc la plus petite possible
- Licence GNU GPL
- Dernière version stable (0.31) : août 2007
newlib
- Vise l'embarqué (mais pas forcément Linux)
- Diverses licences libres (fonctions provenant de divers projets), et une partie sous licence GNU GPL ou GNU LGPL
- Dernière version stable (1.17) : décembre 2008
musl-libc
- small memory footprint
- portable
- fast
- secure
BSD : FreeBSD, OpenBSD, NetBSD, ...
- Licence BSD

LD_BIND_NOT: Flag: if set, Don't update the GOT (global offset table) and PLT (procedure linkage table) after resolving a symbol
LD_BIND_NOW: Flag: Resolve all symbols at program startup, useful with debugger
LD_DEBUG: Output verbose debugging information about the dynamic linker. If set to 'all' prints all debugging information it has, if set to 'help' prints a help message
LD_DEBUG_PATH: Filename for LD_DEBUG output (otherwise it goes to stdout)
LD_LIBRARY_PATH: A colon-separated list of directories in which to search for ELF libraries at execution-time
LD_PRELOAD: A whitespace-separated list of additional, user-specified, ELF shared libraries to be loaded before all others. This can be used to selectively override functions in other shared libraries. For setuid/setgid ELF binaries, only libraries in the standard search directories that are also setuid will be loaded
LD_ORIGIN_PATH : Path where the binary is found
LD_PROFILE : Shared object to be profiled
LD_PROFILE_OUTPUT : File where LD_PROFILE output should be stored, default is stdout
LD_TRACE_LOADED_OBJECTS Flag: if set, list dependencies instead of running (like ldd!)
LD_WARN Flag: if set, warn about about undefined symbols
LD_VERBOSE Flag: If set, output symbol versioning information about the program if querying information about it (see LD_TRACE_LOADED_OBJECTS)

Pour plus d'information sur le linker dynamique, lire « man ld.so ».

SEGFAULT_SIGNALS: List of signals generating segfault: segv, ill, bus, stkflt, abrt, fpe
SEGFAULT_USE_ALTSTACK: Flag: if set, allocate separate stack for segfaults

Note: 'catchsegv' is a shell script coming with glibc which LD_PRELOADs binaries with segfault library understanding above variables.

SEGFAULT_OUTPUT_NAME : Name of the output (backtrace etc) file (default is stderr)
MALLOC_CHECK_ : Set what to do when corrupt pointer is detected with malloc debugging:
- 0: do nothing
- 1: print an error message (default)
- 2: call abort()
MSGVERB SEV_LEVEL : Mask of msgfmt() values to print (label, severity, text, action, tag) and severity level setting for msgfmt()
GMON_OUT_PREFIX : Change -pg (gcc profiling option) output file from default 'gmon.out' to"${GMON_OUT_PREFIX}.${PID}"

LC_CTYPE: Character classification and case conversion
LC_TIME Date and time formats
...
LC_MESSAGES: Formats of informative and diagnostic messages and interactive responses
LC_ALL: Overrides the locales selected by other LC_* variables
LANG: Which message catalog to use
LANGUAGE: Overrides LANG and LC_* settings for message catalogs