Re: [PR debug/77773] segfault when compiling __simd64_float16_t with -g

[Aldy Hernandez]

On 10/27/2016 12:35 AM, Richard Biener wrote:

On Wed, Oct 26, 2016 at 9:17 PM, Aldy Hernandez <al...@redhat.com> wrote:

The following one-liner segfaults on arm-eabi when compiled with
-mfloat-abi=hard -g:

        __simd64_float16_t usingit;

The problem is that the pretty printer (in simple_type_specificer()) is
dereferencing a NULL result from c_common_type_for_mode:

          int prec = TYPE_PRECISION (t);
          if (ALL_FIXED_POINT_MODE_P (TYPE_MODE (t)))
            t = c_common_type_for_mode (TYPE_MODE (t), TYPE_SATURATING (t));
          else
            t = c_common_type_for_mode (TYPE_MODE (t), TYPE_UNSIGNED (t));
          if (TYPE_NAME (t))

The type in question is:

        <real_type 0x7fffefdeb150 HF ...>

which corresponds to HFmode and which AFAICT, does not have a type by
design.

I see that other uses of *type_for_node() throughout the compiler check the
result for NULL, so perhaps we should do the same here.

The attached patch fixes the problem.

OK for trunk?

Your added assert shows another possible issue - can you fix this by assigning
the result of c_common_type_for_mode to a new variable, like common_t and
use that for the TYPE_NAME (...) case?  I think this was what was intended.

Certainly.

OK pending tests?

Aldy

commit 1b914820aca7fa82079622b7ba1f7b01b1e79344
Author: Aldy Hernandez <al...@redhat.com>
Date:   Wed Oct 26 12:06:09 2016 -0700

        PR debug/77773
        * c-pretty-print.c (simple_type_specifier): Do not dereference `t'
        if NULL.

diff --git a/gcc/c-family/c-pretty-print.c b/gcc/c-family/c-pretty-print.c
index 90428ca..7ad5900 100644
--- a/gcc/c-family/c-pretty-print.c
+++ b/gcc/c-family/c-pretty-print.c
@@ -344,14 +344,17 @@ c_pretty_printer::simple_type_specifier (tree t)
       else
        {
          int prec = TYPE_PRECISION (t);
+         tree common_t;
          if (ALL_FIXED_POINT_MODE_P (TYPE_MODE (t)))
-           t = c_common_type_for_mode (TYPE_MODE (t), TYPE_SATURATING (t));
+           common_t = c_common_type_for_mode (TYPE_MODE (t),
+                                              TYPE_SATURATING (t));
          else
-           t = c_common_type_for_mode (TYPE_MODE (t), TYPE_UNSIGNED (t));
-         if (TYPE_NAME (t))
+           common_t = c_common_type_for_mode (TYPE_MODE (t),
+                                              TYPE_UNSIGNED (t));
+         if (common_t && TYPE_NAME (common_t))
            {
-             simple_type_specifier (t);
-             if (TYPE_PRECISION (t) != prec)
+             simple_type_specifier (common_t);
+             if (TYPE_PRECISION (common_t) != prec)
                {
                  pp_colon (this);
                  pp_decimal_int (this, prec);