diff options
Diffstat (limited to 'FAQ')
| -rw-r--r-- | FAQ | 119 |
1 files changed, 117 insertions, 2 deletions
@@ -55,6 +55,14 @@ please let me know. libc anymore?'' [Q15] ``What are these `add-ons'?'' + +[Q16] ``When I use GNU libc on my Linux system by linking against + to libc.so which comes with glibc all I get is a core dump.'' + +[Q17] ``Looking through the shared libc file I haven't found the + functions `stat', `lstat', `fstat', and `mknod' and while + linking on my Linux system I get error messages. How is + this supposed to work?'' ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ [Q1] ``What systems does the GNU C Library run on?'' @@ -425,12 +433,119 @@ to use this feature. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ +[Q16] ``When I use GNU libc on my Linux system by linking against + to libc.so which comes with glibc all I get is a core dump.'' + +[A16] {UD} It is not enough to simply link against the GNU libc +library itself. The GNU C library comes with its own dynamic linker +which really conforms to the ELF API standard. This dynamic linker +must be used. + +Normally this is done by the compiler. The gcc will use + + -dynamic-linker /lib/ld-linux.so.1 + +unless the user specifies her/himself a -dynamic-linker argument. But +this is not the correct name for the GNU dynamic linker. The correct +name is /lib/ld.so.1 which is the name specified in the SVr4 ABi. + +To change your environment to use GNU libc for compiling you need to +change the `specs' file of your gcc. This file is normally found at + + /usr/lib/gcc-lib/<arch>/<version>/specs + +In this file you have to change a few things: + +- change `ld-linux.so.1' to `ld.so.1' + +- remove all expression `%{...:-lgmon}'; there is no libgmon in glibc + + +Things are getting a bit more complicated if you have GNU libc +installed in some other place than /usr, i.e., if you do not want to +use it instead of the old libc. In this case the needed startup files +and libraries are not found in the regular places. So the specs file +must tell the compiler and linker exactly what to use. Here is for +example the gcc-2.7.2 specs file when GNU libc is installed at +/home/gnu: + +----------------------------------------------------------------------- +*asm: +%{V} %{v:%{!V:-V}} %{Qy:} %{!Qn:-Qy} %{n} %{T} %{Ym,*} %{Yd,*} %{Wa,*:%*} + +*asm_final: +%{pipe:-} + +*cpp: +%{fPIC:-D__PIC__ -D__pic__} %{fpic:-D__PIC__ -D__pic__} %{!m386:-D__i486__} %{posix:-D_POSIX_SOURCE} -I/home/gnu/include + +*cc1: + + +*cc1plus: + + +*endfile: +%{!shared:crtend.o%s} %{shared:crtendS.o%s} /home/gnu/lib/crtn.o%s + +*link: +-m elf_i386 -rpath=/home/gnu/lib -L/home/gnu/lib %{shared:-shared} %{!shared: %{!ibcs: %{!static: %{rdynamic:-export-dynamic} %{!dynamic-linker:-dynamic-linker=/home/gnu/lib/ld.so.1}} %{static:-static}}} + +*lib: +%{!shared: %{mieee-fp:-lieee} %{p:-lc_p} %{!p:%{pg:-lc_p} %{!pg:-lc}}} + +*libgcc: +%{!shared:-lgcc} + +*startfile: +%{!shared: %{pg:/home/gnu/lib/gcrt1.o%s} %{!pg:%{p:/home/gnu/lib/gcrt1.o} %{!p:/home/gnu/lib/crt1.o%s}}} /home/gnu/lib/crti.o%s %{!shared:crtbegin.o%s} %{shared:crtbeginS.o%s} + +*switches_need_spaces: + + +*signed_char: +%{funsigned-char:-D__CHAR_UNSIGNED__} + +*predefines: +-D__ELF__ -Dunix -Di386 -Dlinux -Asystem(unix) -Asystem(posix) -Acpu(i386) -Amachine(i386) + +*cross_compile: +0 + +*multilib: +. ; + +----------------------------------------------------------------------- + +Future versions of GCC will automatically provide the correct specs. + + +~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ +[Q17] ``Looking through the shared libc file I haven't found the + functions `stat', `lstat', `fstat', and `mknod' and while + linking on my Linux system I get error messages. How is + this supposed to work?'' + +[A17] {RM} Believe it or not, stat and lstat (and fstat, and mknod) +are supposed to be undefined references in libc.so.6! Your problem is +probably a missing or incorrect /usr/lib/libc.so file; note that this +is a small text file now, not a symlink to libc.so.6. It should look +something like this: + +GROUP ( libc.so.6 ld.so.1 libc.a ) + + +{UD} The Linux ldconfig file probably generates a link libc.so -> +libc.so.6 in /lib. This is not correct. There must not be such a +link. The linker script with the above contents is placed in +/usr/lib which is enough for the linker. + + +~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Answers were given by: {UD} Ulrich Drepper, <drepper@cygnus.com> {DMT} David Mosberger-Tang, <davidm@AZStarNet.com> - -Amended by: {RM} Roland McGrath, <roland@gnu.ai.mit.edu> Local Variables: |