[Emacs-diffs] emacs-26 c911b27: Change GCALIGNMENT back to an integer literal

[Paul Eggert]

branch: emacs-26
commit c911b27aff8dd15cd47a063dc958e6dae74dde06
Author: Paul Eggert <address@hidden>
Commit: Paul Eggert <address@hidden>

    Change GCALIGNMENT back to an integer literal
    
    * src/lisp.h (GCALIGNMENT): Change it back to a macro
    that expands to a literal integer constant, for older GCC.
    I had mistakenly thought that only MSVC had the problem.
    Problem repored by Eli Zaretskii (Bug#29040#69).
---
 src/lisp.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/lisp.h b/src/lisp.h
index a71ba22..4dd4720 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -233,7 +233,9 @@ extern bool suppress_checking EXTERNALLY_VISIBLE;
 
 enum Lisp_Bits
   {
-    GCALIGNMENT = 1 << GCTYPEBITS,
+    /* 2**GCTYPEBITS.  This must be a macro that expands to a literal
+       integer constant, for older versions of GCC (through at least 4.9).  */
+#define GCALIGNMENT 8
 
     /* Number of bits in a Lisp_Object value, not counting the tag.  */
     VALBITS = EMACS_INT_WIDTH - GCTYPEBITS,
@@ -245,6 +247,10 @@ enum Lisp_Bits
     FIXNUM_BITS = VALBITS + 1
   };
 
+#if GCALIGNMENT != 1 << GCTYPEBITS
+# error "GCALIGNMENT and GCTYPEBITS are inconsistent"
+#endif
+
 /* The maximum value that can be stored in a EMACS_INT, assuming all
    bits other than the type bits contribute to a nonnegative signed value.
    This can be used in #if, e.g., '#if USE_LSB_TAG' below expands to an