[Bug bootstrap/64256] [5.0 Regression] Pointer Bounds Checker builtins enum overflows stabstring length

["dje at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64256

--- Comment #10 from David Edelsohn <dje at gcc dot gnu.org> ---
Stabstring continuations originally seem to have been disabled for AIX XCOFF
because the AIX assembler did not support them correctly.  IBM's proprietary
compiler, VAC/XLC, directly generates object files and does not use the AIX
assembler.  XLC produces assembly language files by invoking a disassembler on
the object file.

The AIX XCOFF documentation and stabstring grammar defined continuations, XLC
produced them, the disassembler displayed them, AIX ld supported them, AIX DBX
supported them, but AIX Assembler did not.  No one manually wrote assembly
language files with long enough stabstrings (or any stabstrings) to trip over
the bug.

GCC is the biggest user of the AIX assembler.

At some point the AIX assembler was fixed and now properly supports stabstring
continuations.  As Zoltan mentioned, XLC seems to limit stabstrings to 16K.  XL
disassembler also uses '?' as the continuation character.  GDB accepts '?' as
an alternate continuation character, in addition to '\\'.  On AIX, it is safer
to produce code similar to XLC because the rest of the AIX tools consume that
and problems can be reproduced with native tools, ensuring fixes.

I will test the following patch

Index: xcoffout.h
===================================================================
--- xcoffout.h  (revision 220457)
+++ xcoffout.h  (working copy)
@@ -161,9 +161,12 @@
 /* Do not emit any marker for XCOFF until assembler allows XFT_CV.  */
 #define NO_DBX_GCC_MARKER

-/* Do not break .stabs pseudos into continuations.  */
-#define DBX_CONTIN_LENGTH 0
+/* XCOFF32 maximum length is 64K; XLC limits to 16K.  */
+#define DBX_CONTIN_LENGTH 16384

+/* XLC uses '?' as continuation character.  */
+#define DBX_CONTIN_CHAR '?'
+
 /* Don't try to use the `x' type-cross-reference character in DBX data.
    Also has the consequence of putting each struct, union or enum
    into a separate .stabs, containing only cross-refs to the others.  */