Don't write out static consts now, unless we need them.

From-SVN: r7194

diff --git a/gcc/toplev.c b/gcc/toplev.c
index e6918c8f309b8e7e507751e6906f28d7c6fc04b7..5d516e6536691b752bdc8ca92633b9efa9499e78 100644 (file)
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -2274,14 +2274,33 @@ compile_file (name)
        if (TREE_CODE (decl) == VAR_DECL && TREE_STATIC (decl)
            && ! TREE_ASM_WRITTEN (decl))
          {
-           /* Don't write out static consts, unless we used them.
-              (This used to write them out only if the address was
-              taken, but that was wrong; if the variable was simply
-              referred to, it still needs to exist or else it will
-              be undefined in the linker.)  */
+           /* Don't write out static consts, unless we still need them.
+
+              We also keep static consts if not optimizing (for debugging).
+              ??? They might be better written into the debug information.
+              This is possible when using DWARF.
+
+              A language processor that wants static constants to be always
+              written out (even if it is not used) is responsible for
+              calling rest_of_decl_compilation itself.  E.g. the C front-end
+              calls rest_of_decl_compilation from finish_decl.
+              One motivation for this is that is conventional in some
+              environments to write things like:
+                  static const char rcsid[] = "... version string ...";
+              intending to force the string to be in the executable.
+
+              A language processor that would prefer to have unneeded
+              static constants "optimized away" would just defer writing
+              them out until here.  E.g. C++ does this, because static
+              constants are often defined in header files.
+
+              ??? A tempting alternative (for both C and C++) would be
+              to force a constant to be written if and only if it is
+              defined in a main file, as opposed to an include file. */
+
            if (! TREE_READONLY (decl)
                || TREE_PUBLIC (decl)
-               || TREE_USED (decl)
+               || !optimize
                || TREE_ADDRESSABLE (decl)
                || TREE_ADDRESSABLE (DECL_ASSEMBLER_NAME (decl)))
              rest_of_decl_compilation (decl, NULL_PTR, 1, 1);