Port the GDB-visible symbols to AIX.

Without them, GDB doesn't work to debug Emacs, since the AIX linker
optimizes away the relevant external symbols.  Use enums instead;
this suffices for the AIX port, which is 32-bit-only anyway.
* lisp.h (ENUMABLE, DEFINE_GDB_SYMBOL_ENUM): New macros.
(ARRAY_MARK_FLAG, PSEUDOVECTOR_FLAG, VALMASK): Use them.
(ARRAY_MARK_FLAG_val, PSEUDOVECTOR_FLAG_val, VALMASK_val):
New macros.

2 files changed, 38 insertions, 4 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 4e68b1b8452..2a3625b95da 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,14 @@
+2014-05-29  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Port the GDB-visible symbols to AIX.
+        Without them, GDB doesn't work to debug Emacs, since the AIX linker
+        optimizes away the relevant external symbols.  Use enums instead;
+        this suffices for the AIX port, which is 32-bit-only anyway.
+        * lisp.h (ENUMABLE, DEFINE_GDB_SYMBOL_ENUM): New macros.
+        (ARRAY_MARK_FLAG, PSEUDOVECTOR_FLAG, VALMASK): Use them.
+        (ARRAY_MARK_FLAG_val, PSEUDOVECTOR_FLAG_val, VALMASK_val):
+        New macros.
+
 2014-05-26  Paul Eggert  <eggert@cs.ucla.edu>
 
         Include sources used to create macuvs.h.
diff --git a/src/lisp.h b/src/lisp.h
index c7fc5962349..af54887a51a 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -36,14 +36,21 @@ INLINE_HEADER_BEGIN
 
 /* Define a TYPE constant ID as an externally visible name.  Use like this:
 
+      #define ID_val (some integer preprocessor expression)
+      #if ENUMABLE (ID_val)
+      DEFINE_GDB_SYMBOL_ENUM (ID)
+      #else
       DEFINE_GDB_SYMBOL_BEGIN (TYPE, ID)
-      #define ID something
+      # define ID ID_val
       DEFINE_GDB_SYMBOL_END (ID)
+      #endif
 
    This hack is for the benefit of compilers that do not make macro
    definitions visible to the debugger.  It's used for symbols that
    .gdbinit needs, symbols whose values may not fit in 'int' (where an
    enum would suffice).  */
+#define ENUMABLE(val) (INT_MIN <= (val) && (val) <= INT_MAX)
+#define DEFINE_GDB_SYMBOL_ENUM(id) enum { id = id##_val };
 #if defined MAIN_PROGRAM
 # define DEFINE_GDB_SYMBOL_BEGIN(type, id) type const id EXTERNALLY_VISIBLE
 # define DEFINE_GDB_SYMBOL_END(id) = id;
@@ -571,15 +578,25 @@ LISP_MACRO_DEFUN (XIL, Lisp_Object, (EMACS_INT i), (i))
 
 /* In the size word of a vector, this bit means the vector has been marked.  */
 
+#define ARRAY_MARK_FLAG_val PTRDIFF_MIN
+#if ENUMABLE (ARRAY_MARK_FLAG_val)
+DEFINE_GDB_SYMBOL_ENUM (ARRAY_MARK_FLAG)
+#else
 DEFINE_GDB_SYMBOL_BEGIN (ptrdiff_t, ARRAY_MARK_FLAG)
-#define ARRAY_MARK_FLAG PTRDIFF_MIN
+# define ARRAY_MARK_FLAG ARRAY_MARK_FLAG_val
 DEFINE_GDB_SYMBOL_END (ARRAY_MARK_FLAG)
+#endif
 
 /* In the size word of a struct Lisp_Vector, this bit means it's really
    some other vector-like object.  */
+#define PSEUDOVECTOR_FLAG_val (PTRDIFF_MAX - PTRDIFF_MAX / 2)
+#if ENUMABLE (PSEUDOVECTOR_FLAG_val)
+DEFINE_GDB_SYMBOL_ENUM (PSEUDOVECTOR_FLAG)
+#else
 DEFINE_GDB_SYMBOL_BEGIN (ptrdiff_t, PSEUDOVECTOR_FLAG)
-#define PSEUDOVECTOR_FLAG (PTRDIFF_MAX - PTRDIFF_MAX / 2)
+# define PSEUDOVECTOR_FLAG PSEUDOVECTOR_FLAG_val
 DEFINE_GDB_SYMBOL_END (PSEUDOVECTOR_FLAG)
+#endif
 
 /* In a pseudovector, the size field actually contains a word with one
    PSEUDOVECTOR_FLAG bit set, and one of the following values extracted
@@ -641,9 +658,15 @@ enum More_Lisp_Bits
    XCONS (tem) is the struct Lisp_Cons * pointing to the memory for
    that cons.  */
 
+/* Mask for the value (as opposed to the type bits) of a Lisp object.  */
+#define VALMASK_val (USE_LSB_TAG ? - (1 << GCTYPEBITS) : VAL_MAX)
+#if ENUMABLE (VALMASK_val)
+DEFINE_GDB_SYMBOL_ENUM (VALMASK)
+#else
 DEFINE_GDB_SYMBOL_BEGIN (EMACS_INT, VALMASK)
-#define VALMASK (USE_LSB_TAG ? - (1 << GCTYPEBITS) : VAL_MAX)
+# define VALMASK VALMASK_val
 DEFINE_GDB_SYMBOL_END (VALMASK)
+#endif
 
 /* Largest and smallest representable fixnum values.  These are the C
    values.  They are macros for use in static initializers.  */