[Bug target/29487] Shared libstdc++ fails to link

[bonzini at gnu dot org]

------- Comment #34 from bonzini at gnu dot org  2007-02-06 10:41 -------
The two bits were actually the same, since passes.c was doing this exactly
after calling set_nothrow_function_flags

  if (current_function_nothrow)
    /* Now we know that this can't throw; set the flag for the benefit
       of other functions later in this translation unit.  */
    TREE_NOTHROW (current_function_decl) = 1;

The patch I proposed does not hinder optimization "that much". Declaring a
function as nothrow will still enable optimizations in the callers that depend
on the the callee to be nothrow, as far as the callee binds locally; this
includes static functions, non-default visibility functions, and locally
declared non-weak functions.

Richard, another necessary hunk for correctness would be this:

Index: cvs/gcc/gcc/tree-eh.c
===================================================================
--- cvs/gcc/gcc/tree-eh.c       (revision 120669)
+++ cvs/gcc/gcc/tree-eh.c       (working copy)
@@ -1979,8 +1979,7 @@ tree_could_trap_p (tree expr)

     case CALL_EXPR:
       t = get_callee_fndecl (expr);
-      /* Assume that calls to weak functions may trap.  */
-      if (!t || !DECL_P (t) || DECL_WEAK (t))
+      if (!t || !DECL_P (t) || !targetm.binds_local_p (t))
        return true;
       return false;



Finally, let me remark again that I'm *no expert in this area*.  I'd be pretty
nervous if this patch ended up in 4.1.2 without huge scrutiny from experts.

I'll prepare a patch to revert my 2004 change too.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29487