[C PATCH] Fix ubsan -fsanitize=float-cast-overflow ICE (PR sanitizer/88426)

[Jakub Jelinek]

Hi!

The following testcase ICEs since the c_save_expr removal.  Unlike other
spots where we use save_expr and potentially pass that to function ubsan
calls, in this case we weren't calling c_fully_fold and
c_fully_fold_internal unfortunately doesn't recurse into CALL_EXPRs, so
the gimplifier then sees C_MAYBE_CONST_EXPRs and ICEs on them.  E.g.
for shift sanitization etc. we call c_fully_fold like this.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2018-12-11  Jakub Jelinek  <ja...@redhat.com>

        PR sanitizer/88426
        * c-convert.c (convert): Call c_fully_fold before calling
        ubsan_instrument_float_cast.

        * c-c++-common/ubsan/float-cast-overflow-11.c: New test.

--- gcc/c/c-convert.c.jj        2018-01-03 10:20:20.119537950 +0100
+++ gcc/c/c-convert.c   2018-12-10 09:26:57.846455754 +0100
@@ -115,6 +115,7 @@ convert (tree type, tree expr)
          && COMPLETE_TYPE_P (type))
        {
          expr = save_expr (expr);
+         expr = c_fully_fold (expr, false, NULL);
          tree check = ubsan_instrument_float_cast (loc, type, expr);
          expr = fold_build1 (FIX_TRUNC_EXPR, type, expr);
          if (check == NULL_TREE)
--- gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-11.c.jj        
2018-12-10 09:30:05.548386877 +0100
+++ gcc/testsuite/c-c++-common/ubsan/float-cast-overflow-11.c   2018-12-10 
09:29:49.027656990 +0100
@@ -0,0 +1,10 @@
+/* PR sanitizer/88426 */
+/* { dg-do compile } */
+/* { dg-options "-fsanitize=float-cast-overflow" } */
+
+int
+foo (void)
+{
+  const float v = 0.0f;
+  return (int) (v < 0.0f ? v : 0.0f);
+}

        Jakub