Hi Alex, Hi Jeff, Hi Richard,
Consider the following small test case:
% cat test1.c
extern int g (void) __attribute__ ((visibility("protected")));
int f (void) { return g (); }
% cat test2.c
extern int g(void) __attribute__ ((visibility("protected")));
int i;
int g (void) { return i; }
% gcc -fPIC -c test1.c test2.c
% gcc -shared -o libtest_protected.so test1.o test2.o
When compiled with a MN10300 toolchain based on the current FSF GCC
and binutils sources the final link will fail with:
test1.o: In function `f':
test1.c:(.text+0x7): warning: error: inappropriate relocation type for
shared library (did you forget -fpic?)
The problem here is that GCC has decided that since "g" is protected
it does not need a PLT entry. But the linker has decided that since
"g" is a function it does need a PLT entry (even though it is
protected) so that function pointer comparison will work. (See the
definition of SYMBOL_REFERENCES_LOCAL in bfd/elf-bfd.h for more
information on this).
I have a small patch that fixes this problem (see below), but I am not
sure if this is the correct solution. As far as I can see, this is
not an MN10300 specific problem however, so surely other targets ought
to have similar problems ? (But other targets do not seem to use
targetm.binds_local_p to decide if a symbol is global or local. cf/
mn10300_encode_section_info).
Anyway any advice or comments on the situation would be appreciated.
Cheers
Nick
Index: gcc/config/mn10300/mn10300.c
===================================================================
--- gcc/config/mn10300/mn10300.c (revision 174069)
+++ gcc/config/mn10300/mn10300.c (working copy)
@@ -3315,8 +3315,30 @@
}
}
+static bool
+mn10300_binds_local (const_tree exp)
+{
+ bool local = default_binds_local_p (exp);
+
+ /* The default binds_local function will decide that protected functions
+ bind locally. Whilst technically this is true, in practice in PIC mode
+ protected functions still need a PLT entry so that function pointer
+ comparison will work. */
+ if (local
+ && flag_pic
+ && DECL_P (exp)
+ && TREE_CODE (exp) == FUNCTION_DECL
+ && DECL_VISIBILITY (exp) == VISIBILITY_PROTECTED)
+ return false;
+
+ return local;
+}
+
/* Initialize the GCC target structure. */
+#undef TARGET_BINDS_LOCAL_P
+#define TARGET_BINDS_LOCAL_P mn10300_binds_local
+
#undef TARGET_MACHINE_DEPENDENT_REORG
#define TARGET_MACHINE_DEPENDENT_REORG mn10300_reorg
