Fix a bug that caused incorrect PIC code to be generated for exceptions.

The symptom was an assembler warning

    "GOT relocation burb: `___EXCEPTION_TABLE__' should be global"

followed (sometimes) by a core dump.  The fix makes the compiler
generate the correct GOTOFF addressing for that symbol, rather than the
GOT addressing it was emitting before.

Warning:  There is still at least one serious bug in the i386 exception
code for PIC.  The exception code that is generated clobbers the GOT
register (%ebx) and then tries to use it later.  That leads to core
dumps at program execution time.  I know where the problem is, but I do
not have a fix for it at this time.  Until it is fixed, exceptions will
not work in PIC code.  This is a general problem for all i386 platforms;
it is not specific to FreeBSD.

2 files changed, 23 insertions, 1 deletions

diff --git a/contrib/gcc/config/i386/i386.h b/contrib/gcc/config/i386/i386.h
index b00b0e5..efc956a 100644
--- a/contrib/gcc/config/i386/i386.h
+++ b/contrib/gcc/config/i386/i386.h
@@ -1286,6 +1286,22 @@ do									\
   }									\
 while (0)
 
+/* Define this macro if a SYMBOL_REF representing a non-global
+   address must be marked specially.  This is called for
+   compiler-generated local symbols, such as "__EXCEPTION_TABLE__".
+
+   On i386, if using PIC, we use this to set the rtx's
+   SYMBOL_REF_FLAG, so that we may access it directly as
+   an offset from the GOT register. */
+
+#define MARK_LOCAL_ADDRESS(X)						\
+do									\
+  {									\
+    if (flag_pic && GET_CODE (X) == SYMBOL_REF)				\
+      SYMBOL_REF_FLAG (X) = 1;						\
+  }									\
+while (0)
+
 /* Initialize data used by insn expanders.  This is called from
    init_emit, once for each function, before code is generated.
    For 386, clear stack slot assignments remembered from previous
diff --git a/contrib/gcc/cp/except.c b/contrib/gcc/cp/except.c
index 51577f8..4443b98 100644
--- a/contrib/gcc/cp/except.c
+++ b/contrib/gcc/cp/except.c
@@ -1614,9 +1614,15 @@ emit_exception_table ()
 void
 register_exception_table ()
 {
+  rtx addr = gen_rtx (SYMBOL_REF, Pmode, "__EXCEPTION_TABLE__");
+
+#ifdef MARK_LOCAL_ADDRESS
+  MARK_LOCAL_ADDRESS(addr);
+#endif
+
   emit_library_call (gen_rtx (SYMBOL_REF, Pmode, "__register_exceptions"), 0,
 		     VOIDmode, 1,
-		     gen_rtx (SYMBOL_REF, Pmode, "__EXCEPTION_TABLE__"),
+		     addr,
 		     Pmode);
 }