Fix export of symbols to GDB.

* alloc.c (ARRAY_MARK_FLAG_VAL, PSEUDOVECTOR_FLAG_VAL, VALMASK_VAL)
(ARRAY_MARK_FLAG, PSEUDOVECTOR_FLAG, VALMASK): Move these here from
emacs.c, as this is a more-suitable home.  Had this been done earlier
the fix for 1995-05-30T23:07:27Z!kwzh@gnu.org would have avoided some of the problems noted in
<http://bugs.gnu.org/1995-05-30T23:07:27Z!kwzh@gnu.org#13> by Eli Zaretskii, as the scope problems
would have been more obvious.
* emacs.c (gdb_CHECK_LISP_OBJECT_TYPE, gdb_DATA_SEG_BITS)
(gdb_GCTYPEBITS, gdb_USE_LSB_TAG)
(CHECK_LISP_OBJECT_TYPE, DATA_SEG_BITS, GCTYPEBITS, USE_LSB_TAG):
Remove; now done in lisp.h.
* lisp.h (PUBLISH_TO_GDB): New macro.
(GCTYPEBITS, USE_LSB_TAG, CHECK_LISP_OBJECT_TYPE, enum pvec_type)
(DATA_SEG_BITS): Use it.
(GCTYPEBITS, USE_LSB_TAG): Now also an enum, for GDB.
(CHECK_LISP_OBJECT_TYPE, DATA_SEG_BITS): Now just an enum, for GDB.
* mem-limits.h (EXCEEDS_LISP_PTR): Redo so that DATA_SEG_BITS need
not be usable in #if.  This simplifies things.

5 files changed, 82 insertions, 56 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index b4e5fe84879..06633ba7165 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,24 @@
+2012-07-26  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Fix export of symbols to GDB (Bug#12036).
+        * alloc.c (ARRAY_MARK_FLAG_VAL, PSEUDOVECTOR_FLAG_VAL, VALMASK_VAL)
+        (ARRAY_MARK_FLAG, PSEUDOVECTOR_FLAG, VALMASK): Move these here from
+        emacs.c, as this is a more-suitable home.  Had this been done earlier
+        the fix for 12036 would have avoided some of the problems noted in
+        <http://bugs.gnu.org/12036#13> by Eli Zaretskii, as the scope problems
+        would have been more obvious.
+        * emacs.c (gdb_CHECK_LISP_OBJECT_TYPE, gdb_DATA_SEG_BITS)
+        (gdb_GCTYPEBITS, gdb_USE_LSB_TAG)
+        (CHECK_LISP_OBJECT_TYPE, DATA_SEG_BITS, GCTYPEBITS, USE_LSB_TAG):
+        Remove; now done in lisp.h.
+        * lisp.h (PUBLISH_TO_GDB): New macro.
+        (GCTYPEBITS, USE_LSB_TAG, CHECK_LISP_OBJECT_TYPE, enum pvec_type)
+        (DATA_SEG_BITS): Use it.
+        (GCTYPEBITS, USE_LSB_TAG): Now also an enum, for GDB.
+        (CHECK_LISP_OBJECT_TYPE, DATA_SEG_BITS): Now just an enum, for GDB.
+        * mem-limits.h (EXCEEDS_LISP_PTR): Redo so that DATA_SEG_BITS need
+        not be usable in #if.  This simplifies things.
+
 2012-07-26  Juanma Barranquero  <lekktu@gmail.com>
 
         * makefile.w32-in ($(BLD)/emacs.$(O)): Update dependencies.
diff --git a/src/alloc.c b/src/alloc.c
index d9c56b5c7c8..ac6cb861c4d 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -6875,3 +6875,29 @@ The time is in seconds as a floating point value.  */);
   defsubr (&Sgc_status);
 #endif
 }
+
+/* Make some symbols visible to GDB.  These cannot be done as enums, like
+   GCTYPEBITS or USE_LSB_TAG, since values might not be in 'int' range.
+   Each symbol X has a corresponding X_VAL symbol, verified to have
+   the correct value.
+
+   This is last, so that the #undef lines don't mess up later code.  */
+
+#define ARRAY_MARK_FLAG_VAL PTRDIFF_MIN
+#define PSEUDOVECTOR_FLAG_VAL (PTRDIFF_MAX - PTRDIFF_MAX / 2)
+#define VALMASK_VAL (USE_LSB_TAG ? -1 << GCTYPEBITS : VAL_MAX)
+
+verify (ARRAY_MARK_FLAG_VAL == ARRAY_MARK_FLAG);
+verify (PSEUDOVECTOR_FLAG_VAL == PSEUDOVECTOR_FLAG);
+verify (VALMASK_VAL == VALMASK);
+
+#undef ARRAY_MARK_FLAG
+#undef PSEUDOVECTOR_FLAG
+#undef VALMASK
+
+ptrdiff_t const EXTERNALLY_VISIBLE
+  ARRAY_MARK_FLAG = ARRAY_MARK_FLAG_VAL,
+  PSEUDOVECTOR_FLAG = PSEUDOVECTOR_FLAG_VAL;
+
+EMACS_INT const EXTERNALLY_VISIBLE
+  VALMASK = VALMASK_VAL;
diff --git a/src/emacs.c b/src/emacs.c
index c737a41974f..7dad87ef38b 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -2490,50 +2490,3 @@ libraries; only those already known by Emacs will be loaded.  */);
   /* Make sure IS_DAEMON starts up as false.  */
   daemon_pipe[1] = 0;
 }
-
-/* Make these values available in GDB, which doesn't see macros.
-   This is last, so that the #undef lines don't mess up later code.  */
-
-enum
-  {
-    gdb_CHECK_LISP_OBJECT_TYPE = CHECK_LISP_OBJECT_TYPE,
-    gdb_DATA_SEG_BITS = DATA_SEG_BITS,
-    gdb_GCTYPEBITS = GCTYPEBITS,
-    gdb_USE_LSB_TAG = USE_LSB_TAG
-  };
-
-#undef CHECK_LISP_OBJECT_TYPE
-#undef DATA_SEG_BITS
-#undef GCTYPEBITS
-#undef USE_LSB_TAG
-
-enum
-  {
-    CHECK_LISP_OBJECT_TYPE = gdb_CHECK_LISP_OBJECT_TYPE,
-    DATA_SEG_BITS = gdb_DATA_SEG_BITS,
-    GCTYPEBITS = gdb_GCTYPEBITS,
-    USE_LSB_TAG = gdb_USE_LSB_TAG
-  };
-
-/* These are trickier since they might fall out of int range.  Each
-   symbol X has a corresponding X_VAL symbol, verified to have the
-   correct value.  */
-
-#define ARRAY_MARK_FLAG_VAL PTRDIFF_MIN
-#define PSEUDOVECTOR_FLAG_VAL (PTRDIFF_MAX - PTRDIFF_MAX / 2)
-#define VALMASK_VAL (USE_LSB_TAG ? -1 << GCTYPEBITS : VAL_MAX)
-
-verify (ARRAY_MARK_FLAG_VAL == ARRAY_MARK_FLAG);
-verify (PSEUDOVECTOR_FLAG_VAL == PSEUDOVECTOR_FLAG);
-verify (VALMASK_VAL == VALMASK);
-
-#undef ARRAY_MARK_FLAG
-#undef PSEUDOVECTOR_FLAG
-#undef VALMASK
-
-ptrdiff_t const EXTERNALLY_VISIBLE
-  ARRAY_MARK_FLAG = ARRAY_MARK_FLAG_VAL,
-  PSEUDOVECTOR_FLAG = PSEUDOVECTOR_FLAG_VAL;
-
-EMACS_INT const EXTERNALLY_VISIBLE
-  VALMASK = VALMASK_VAL;
diff --git a/src/lisp.h b/src/lisp.h
index 8f309617e69..f845ea6bd12 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -64,6 +64,12 @@ typedef unsigned int EMACS_UINT;
 # endif
 #endif
 
+/* If an enum type is not used, the enum symbols are not put into the
+   executable so the debugger cannot see them on many systems, e.g.,
+   GCC 4.7.1 + GDB 7.4.1 + GNU/Linux.  Work around this problem by
+   explicitly using the names in the integer constant expression EXPR.  */
+#define PUBLISH_TO_GDB(expr) extern int (*gdb_dummy (int))[(expr) || 1]
+
 /* Number of bits in some machine integer types.  */
 enum
   {
@@ -155,7 +161,10 @@ extern int suppress_checking EXTERNALLY_VISIBLE;
    variable VAR of type TYPE with the added requirement that it be
    TYPEBITS-aligned.  */
 
-/* Number of bits in a Lisp_Object tag.  This can be used in #if.  */
+/* Number of bits in a Lisp_Object tag.  This can be used in #if,
+   and for GDB's sake also as a regular symbol.  */
+enum { GCTYPEBITS = 3 };
+PUBLISH_TO_GDB (GCTYPEBITS);
 #define GCTYPEBITS 3
 
 /* Number of bits in a Lisp_Object value, not counting the tag.  */
@@ -202,7 +211,16 @@ enum { VALBITS = BITS_PER_EMACS_INT - GCTYPEBITS };
 #  endif
 # endif
 #endif
-#ifndef USE_LSB_TAG
+/* USE_LSB_TAG can be used in #if; default it to 0 and make it visible
+   to GDB.  */
+#ifdef USE_LSB_TAG
+# undef USE_LSB_TAG
+enum { USE_LSB_TAG = 1 };
+PUBLISH_TO_GDB (USE_LSB_TAG);
+# define USE_LSB_TAG 1
+#else
+enum { USE_LSB_TAG = 0 };
+PUBLISH_TO_GDB (USE_LSB_TAG);
 # define USE_LSB_TAG 0
 #endif
 
@@ -317,6 +335,8 @@ LISP_MAKE_RVALUE (Lisp_Object o)
 }
 
 #define LISP_INITIALLY_ZERO {0}
+#undef CHECK_LISP_OBJECT_TYPE
+enum { CHECK_LISP_OBJECT_TYPE = 1 };
 
 #else /* CHECK_LISP_OBJECT_TYPE */
 
@@ -327,8 +347,9 @@ typedef EMACS_INT Lisp_Object;
 #define XIL(i) (i)
 #define LISP_MAKE_RVALUE(o) (0+(o))
 #define LISP_INITIALLY_ZERO 0
-#define CHECK_LISP_OBJECT_TYPE 0
+enum { CHECK_LISP_OBJECT_TYPE = 0 };
 #endif /* CHECK_LISP_OBJECT_TYPE */
+PUBLISH_TO_GDB (CHECK_LISP_OBJECT_TYPE);
 
 /* In the size word of a vector, this bit means the vector has been marked.  */
 
@@ -368,6 +389,7 @@ enum pvec_type
   PVEC_SUB_CHAR_TABLE           = 0x30,
   PVEC_FONT                     = 0x40
 };
+PUBLISH_TO_GDB ((enum pvec_type) 0);  /* This also publishes PVEC_*.  */
 
 /* For convenience, we also store the number of elements in these bits.
    Note that this size is not necessarily the memory-footprint size, but
@@ -386,10 +408,16 @@ enum
 enum { BOOL_VECTOR_BITS_PER_CHAR = 8 };
 
 /* DATA_SEG_BITS forces extra bits to be or'd in with any pointers
-   which were stored in a Lisp_Object */
-#ifndef DATA_SEG_BITS
-# define DATA_SEG_BITS 0
+   which were stored in a Lisp_Object.  It is not needed in #if, so
+   for GDB's sake change it from a macro to a regular symbol.  */
+#ifdef DATA_SEG_BITS
+enum { gdb_DATA_SEG_BITS = DATA_SEG_BITS };
+# undef DATA_SEG_BITS
+enum { DATA_SEG_BITS = gdb_DATA_SEG_BITS };
+#else
+enum { DATA_SEG_BITS = 0 };
 #endif
+PUBLISH_TO_GDB (DATA_SEG_BITS);
 
 /* These macros extract various sorts of values from a Lisp_Object.
  For example, if tem is a Lisp_Object whose type is Lisp_Cons,
diff --git a/src/mem-limits.h b/src/mem-limits.h
index 0376f407217..57a0ca6fefd 100644
--- a/src/mem-limits.h
+++ b/src/mem-limits.h
@@ -36,9 +36,7 @@ extern int etext;
 extern char *start_of_data (void) ATTRIBUTE_CONST;
 #if USE_LSB_TAG || UINTPTR_MAX <= VAL_MAX
 #define EXCEEDS_LISP_PTR(ptr) 0
-#elif DATA_SEG_BITS
+#else
 #define EXCEEDS_LISP_PTR(ptr) \
   (((uintptr_t) (ptr) & ~DATA_SEG_BITS) >> VALBITS)
-#else
-#define EXCEEDS_LISP_PTR(ptr) ((uintptr_t) (ptr) >> VALBITS)
 #endif