Re: [Tinycc-devel] tcc error msg compiling Abiword 2.2.2 - maybe a bug.

[Dave Dodge]

On Fri, Jan 21, 2005 at 06:14:07PM -0600, Parzival Herzog wrote:
> ../wv/decode_simple.c:313: lvalue expected
> make[1]: *** [decode_simple.o] Error 1
> make[1]: Leaving directory `/home/parz/x-src/abiword-2.2.2/wv'

It's a tcc bug.

> A cursory inspection of the code does not help me to find why
> there is a problem here,

It's subtle.  The problem is that the code does this:

  typedef ... SEP;
  typedef ... sep;

  {
     SEP sep;  /* declare a local variable called "sep" via a typedef */
  }

tcc parses "SEP sep" as two typedef names in a row with no variables
to be declared, and simply ignores the statement.  The result is that
the "sep" local variable is never actually declared, and you get an
error any time the function tries to use it.

See below for a patch against tcc 0.9.22 that should fix it.  I
believe this will also fix Enno Rehling's report of the same basic
problem from about a month ago.

                                                  -Dave Dodge

---------------------------------------------------------------

tcc 0.9.22 doesn't properly handle the following construct:

  typedef [...] a;
  typedef [...] b;

  [...] foo([...])
  {
    a b; /* not parsed correctly */
  }

The problem is that it parses both "a" and "b" as typedef names, and
does nothing as a result.  Although the C99 grammar allows this
parsing, there is a constraint in the narrative that invalidates it
and requires "b" to be treated as a declarator.  This patch causes tcc
to stop looking for typedef names in a declaration specifier list
after it finds the first one; the end result should be that "b"
becomes a local variable and hides the "b" typedef while in scope.

--- tcc-0.9.22/tcc.c    2004-11-08 15:47:16.000000000 -0500
+++ tcc-0.9.22-patched/tcc.c    2005-01-24 23:08:04.000000000 -0500
@@ -6497,13 +6497,14 @@
  */
 static int parse_btype(CType *type, AttributeDef *ad)
 {
-    int t, u, type_found, typespec_found;
+    int t, u, type_found, typespec_found, typedef_found;
     Sym *s;
     CType type1;
 
     memset(ad, 0, sizeof(AttributeDef));
     type_found = 0;
     typespec_found = 0;
+    typedef_found = 0;
     t = 0;
     while(1) {
         switch(tok) {
@@ -6638,9 +6639,15 @@
         default:
             if (typespec_found)
                 goto the_end;
+            if (typedef_found)
+                /* we've already found a typedef-name in the declaration */
+                /* specifier list, so ignore any further ones and treat */
+                /* them as plain identifiers */
+                goto the_end;
             s = sym_find(tok);
             if (!s || !(s->type.t & VT_TYPEDEF))
                 goto the_end;
+            typedef_found = 1;
             t |= (s->type.t & ~VT_TYPEDEF);
             type->ref = s->type.ref;
             next();