bug#13650: Emacs pretest 24.2.93 - compilation error on AIX 5.3 using gcc 4.7-2

[Paul Eggert <eggert@cs.ucla.edu>]

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On 02/13/2013 03:33 PM, Glenn Morris wrote:

> since it apparently worked in Emacs 24.2, then in emacs-24
> branch at this stage we should just do the minimum to get
> it back to that working state, and save improvements for trunk.

We can certainly give that a try.  Looking at unexaix.c, the
changes made between 24.2 and 24.2.93 are small.  The first
change to unexaix.c, in emacs-24 bzr 108226
<http://bzr.savannah.gnu.org/lh/emacs/emacs-24/revision/108226>,
fixed a bug privately reported to me by Gilles on
2012-05-09; he already tested this so it shouldn't be the
problem.  The remaining changes are small: it shouldn't hurt
to undo them but the real problem surely lies elsewhere.

I see two main suspects.  First, we got rid of DATA_START
and DATA_SEG_BITS on AIX.  Second, USE_LSB_TAG changed from
0 to 1 on AIX.

And now that I look at the code again, I see a serious bug
in Emacs 24.2.93's src/lisp.h when DATA_SEG_BITS is nonzero:
it mis-defines XPNTR as if DATA_SEG_BITS were zero.  This is a
regression and should be fixed in emacs-24 regardless of the
AIX fixes, I expect.

So: Gilles, can you please try the following?

First, aply the attached patch to a fresh copy of emacs-24.2.93.

Then, run these shell commands:

   ./configure CPPFLAGS='-DDATA_START=0x20000000 -DDATA_SEG_BITS=0x20000000 -DUSE_LSB_TAG=0'
   make

If this works, I'll have some followup questions and
proposed changes; the point of the above is to try to test
reverting to 24.2's approach as quickly and painlessly as
possible, without reverting all the other changes we've
made.


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diff -pru emacs-24.2.93/src/lisp.h emacs-24.2.93-AIX/src/lisp.h
--- emacs-24.2.93/src/lisp.h	2013-01-01 12:37:17.000000000 -0800
+++ emacs-24.2.93-AIX/src/lisp.h	2013-02-13 18:05:17.635430235 -0800
@@ -496,13 +496,9 @@ static EMACS_INT const VALMASK
   (XIL ((EMACS_INT) ((EMACS_UINT) (type) << VALBITS)  \
 	+ ((intptr_t) (ptr) & VALMASK)))
 
-#if DATA_SEG_BITS
 /* DATA_SEG_BITS forces extra bits to be or'd in with any pointers
    which were stored in a Lisp_Object.  */
 #define XPNTR(a) ((uintptr_t) ((XLI (a) & VALMASK)) | DATA_SEG_BITS))
-#else
-#define XPNTR(a) ((uintptr_t) (XLI (a) & VALMASK))
-#endif
 
 #endif /* not USE_LSB_TAG */
 
diff -pru emacs-24.2.93/src/unexaix.c emacs-24.2.93-AIX/src/unexaix.c
--- emacs-24.2.93/src/unexaix.c	2013-01-01 12:37:17.000000000 -0800
+++ emacs-24.2.93-AIX/src/unexaix.c	2013-02-13 18:23:19.179525573 -0800
@@ -57,9 +57,8 @@ what you give them.   Help stamp out sof
 #include <unistd.h>
 #include <fcntl.h>
 
-#include "mem-limits.h"
-
 char *start_of_text (void);		        /* Start of text */
+extern char *start_of_data (void);		/* Start of initialized data */
 
 extern int _data;
 extern int _text;
@@ -90,6 +89,7 @@ static int adjust_lnnoptrs (int, int, co
 
 static int pagemask;
 
+#include <setjmp.h>
 #include "lisp.h"
 
 static void
@@ -104,6 +104,9 @@ report_error (const char *file, int fd)
 #define ERROR1(msg,x) report_error_1 (new, msg, x, 0); return -1
 #define ERROR2(msg,x,y) report_error_1 (new, msg, x, y); return -1
 
+#undef ADDR_CORRECT
+#define ADDR_CORRECT(x) ((int)(x))
+
 static void
 report_error_1 (int fd, const char *msg, int a1, int a2)
 {