| Message ID | 4C910D67.3050809@codesourcery.com |
|---|---|
| State | New |
| Headers | show |
Nathan Sidwell <nathan@codesourcery.com> writes: > Would you like to try this patch? It correctly enables ifunc testing on my > i686-pc-linux-gnu glibc 2.11 system I think this is the wrong approach: if the feature requires linker and/or runtime linker support, the gcc/configure.ac check should check for this and enable or disable it depending on the results. I consider it bad if the compiler accepts the code, only to fall down at link or runtime. And as I've asked before: what is required to make this work: * Assembler support for @gnu_indirect_function (already checked in gcc/configure.ac)? * Linker support? What specifially? * Runtime linker support? Is this the purpose of your glibc 2.11 check: to test for ld.so.1 support? Thanks. Rainer
On 09/16/10 08:51, Rainer Orth wrote: > Nathan Sidwell<nathan@codesourcery.com> writes: > >> Would you like to try this patch? It correctly enables ifunc testing on my >> i686-pc-linux-gnu glibc 2.11 system > > I think this is the wrong approach: if the feature requires linker > and/or runtime linker support, the gcc/configure.ac check should check > for this and enable or disable it depending on the results. I consider > it bad if the compiler accepts the code, only to fall down at link or > runtime. > > And as I've asked before: what is required to make this work: > > * Assembler support for @gnu_indirect_function (already checked in > gcc/configure.ac)? correct > > * Linker support? What specifially? support for the ifunc relocations (both static and dynamic) > * Runtime linker support? Is this the purpose of your glibc 2.11 check: > to test for ld.so.1 support? handling for the ifunc dynamic relocations. nathan
Nathan Sidwell <nathan@codesourcery.com> writes: >> And as I've asked before: what is required to make this work: >> >> * Assembler support for @gnu_indirect_function (already checked in >> gcc/configure.ac)? > > correct >> >> * Linker support? What specifially? > > support for the ifunc relocations (both static and dynamic) Ok, so check for the GNU ld (and eventually gold) version that supports this in gcc/configure.ac, and assume that other linkers don't have that support. If that assumption proves incorrect later, this can be handled on a case-by-case basis. >> * Runtime linker support? Is this the purpose of your glibc 2.11 check: >> to test for ld.so.1 support? > > handling for the ifunc dynamic relocations. No idea what's the best way to check this. Rainer
On Thu, Sep 16, 2010 at 10:16:21AM +0200, Rainer Orth wrote: > Ok, so check for the GNU ld (and eventually gold) version that supports > this in gcc/configure.ac, and assume that other linkers don't have that > support. If that assumption proves incorrect later, this can be handled > on a case-by-case basis. > > >> * Runtime linker support? Is this the purpose of your glibc 2.11 check: > >> to test for ld.so.1 support? > > > > handling for the ifunc dynamic relocations. > > No idea what's the best way to check this. Especially for cross compiling it can't be a runtime test, so the best is to check __GLIBC__ and __GLIBC_MINOR__ IMHO (for the targets that actually support it). Jakub
2010-09-15 Nathan Sidwell <nathan@codesourcery.com> * lib/target-supports-dg.exp (dg-require_ifunc): Remove remnants of dg-require-alias. * lib/target-supports.exp (check_ifunc_available): Check known good GLIBC version. Remove check_alias_available remnants. Index: lib/target-supports-dg.exp =================================================================== --- lib/target-supports-dg.exp (revision 164285) +++ lib/target-supports-dg.exp (working copy) @@ -94,12 +94,7 @@ # test. proc dg-require-ifunc { args } { - set ifunc_available [ check_ifunc_available ] - if { $ifunc_available == -1 } { - upvar name name - unresolved "$name" - } - if { $ifunc_available < 2 } { + if { ![ check_ifunc_available ] } { upvar dg-do-what dg-do-what set dg-do-what [list [lindex ${dg-do-what} 0] "N" "P"] } Index: lib/target-supports.exp =================================================================== --- lib/target-supports.exp (revision 164285) +++ lib/target-supports.exp (working copy) @@ -372,12 +372,10 @@ # proc check_ifunc_available { } ############################### -# Determine if the target toolchain supports the alias attribute. +# Determine if the target toolchain supports the ifunc attribute. -# Returns 2 if the target supports aliases. Returns 1 if the target -# only supports weak aliased. Returns 0 if the target does not -# support aliases at all. Returns -1 if support for aliases could not -# be determined. +# Returns 1 if the target supports ifunc. Returns 0 if the target +# does not support ifunc. proc check_ifunc_available { } { global ifunc_available_saved @@ -390,26 +388,22 @@ set obj ifunc[pid].o verbose "check_ifunc_available compiling testfile $src" 2 set f [open $src "w"] - # Compile a small test program. The definition of "g" is - # necessary to keep the Solaris assembler from complaining - # about the program. - puts $f "#ifdef __cplusplus\nextern \"C\"\n#endif\n" - puts $f "void g() {} void f() __attribute__((ifunc(\"g\")));" + puts $f "#include <features.h>" + puts $f "#if __GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 11)" + puts $f "#error FOO" + puts $f "#endif" + puts $f "#ifdef __cplusplus\nextern \"C\"\n#endif" + puts $f "void g() {}" + puts $f "void f() __attribute__((ifunc(\"g\")));" close $f set lines [${tool}_target_compile $src $obj object ""] file delete $src remote_file build delete $obj if [string match "" $lines] then { - # No error messages, everything is OK. - set ifunc_available_saved 2 + set ifunc_available_saved 1 } else { - if [regexp "ifunc is not supported" $lines] { - verbose "check_ifunc_available target does not support ifunc" 2 - set ifunc_available_saved 0 - } else { - set ifunc_available_saved -1 - } + set ifunc_available_saved 0 } verbose "check_ifunc_available returning $ifunc_available_saved" 2