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| author | Stefan Liebler <stli@linux.vnet.ibm.com> | 2016-10-07 09:56:46 +0200 |
|---|---|---|
| committer | Stefan Liebler <stli@linux.vnet.ibm.com> | 2016-10-07 10:02:59 +0200 |
| commit | 022dfdce000374b60aadfb0a5ed9a5c4c1dbd29b (patch) | |
| tree | 65102672775985613583740ef7e98625043d0298 /manual/install.texi | |
| parent | 1e7c8fcca5ace329f81785bcdfc139a4c93e9de5 (diff) | |
Add configure check to test if gcc supports attribute ifunc.
This patch adds a configure check to test if gcc supports attribute ifunc.
The support can either be enabled in <gcc-src>/gcc/config.gcc for one
architecture in general by setting default_gnu_indirect_function variable to yes
or by configuring gcc with --enable-gnu-indirect-function.
The next patch rewrites libc_ifunc macro to use gcc attribute ifunc instead
of inline assembly to generate the IFUNC symbols due to false debuginfo.
If gcc does not support attribute ifunc, the old approach for generating
ifunc'ed symbols is used. Then the debug-information is false. Thus it is
recommended to use a gcc with indirect function support (See notes in INSTALL).
After this patch-series these inline assemblies for ifunc-handling are not
scattered in multiple files but are used only indirect via ifunc-macros
and can simply removed in libc-symbols.h in future.
If glibc is configured with --enable-multi-arch and gcc does not support
attribute ifunc, a configure warning is dumped!
ChangeLog:
* config.h.in (HAVE_GCC_IFUNC): New undef.
* configure.ac: Add check if gcc supports attribute ifunc feature.
* configure: Regenerated.
* manual/install.texi: Add recommendation for gcc with
indirect-function support.
* INSTALL: Regenerated.
Diffstat (limited to 'manual/install.texi')
| -rw-r--r-- | manual/install.texi | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/manual/install.texi b/manual/install.texi index 663f8d59fb..de1c2030d3 100644 --- a/manual/install.texi +++ b/manual/install.texi @@ -402,6 +402,14 @@ the newest version of the compiler that is known to work for building release time, GCC 5.3 is the newest compiler verified to work to build @theglibc{}. +For multi-arch support it is recommended to use a GCC which has been built with +support for GNU indirect functions. This ensures that correct debugging +information is generated for functions selected by IFUNC resolvers. This +support can either be enabled by configuring GCC with +@samp{--enable-gnu-indirect-function}, or by enabling it by default by setting +@samp{default_gnu_indirect_function} variable for a particular architecture in +the GCC source file @file{gcc/config.gcc}. + You can use whatever compiler you like to compile programs that use @theglibc{}. |