[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 <aldyh@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
-------------- next part --------------
commit 1b914820aca7fa82079622b7ba1f7b01b1e79344
Author: Aldy Hernandez <aldyh@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);