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Further refinement to -Wswitch-unreachable

Message ID 20160531134052.GN3014@redhat.com
State New
Headers show

Commit Message

Marek Polacek May 31, 2016, 1:40 p.m. UTC 
On Fri, May 27, 2016 at 10:41:51AM -0400, Jason Merrill wrote:
> On 05/26/2016 02:44 PM, Marek Polacek wrote:
> > +	  if (gimple_code (stmt) == GIMPLE_TRY)
> >  	    {
> > +	      /* A compiler-generated cleanup or a user-written try block.
> > +		 Try to get the first statement in its try-block, for better
> > +		 location.  */
> > +	      if ((seq = gimple_try_eval (stmt)))
> > +		stmt = gimple_seq_first_stmt (seq);
> 
> Should this loop?  If there are two variables declared, do we get two try
> blocks?

It looks like we get only one try block, so this doesn't have to loop.  But I
at least added a new test to make sure we warn even with more decls.

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

2016-05-31  Marek Polacek  <polacek@redhat.com>

	* gimplify.c (gimplify_switch_expr): Also handle GIMPLE_TRY.

	* c-c++-common/Wswitch-unreachable-3.c: New test.
	* g++.dg/warn/Wswitch-unreachable-1.C: New test.


	Marek

Comments

Jason Merrill May 31, 2016, 2:48 p.m. UTC | #1 
On Tue, May 31, 2016 at 9:40 AM, Marek Polacek <polacek@redhat.com> wrote:
> On Fri, May 27, 2016 at 10:41:51AM -0400, Jason Merrill wrote:
>> On 05/26/2016 02:44 PM, Marek Polacek wrote:
>> > +     if (gimple_code (stmt) == GIMPLE_TRY)
>> >         {
>> > +         /* A compiler-generated cleanup or a user-written try block.
>> > +            Try to get the first statement in its try-block, for better
>> > +            location.  */
>> > +         if ((seq = gimple_try_eval (stmt)))
>> > +           stmt = gimple_seq_first_stmt (seq);
>>
>> Should this loop?  If there are two variables declared, do we get two try
>> blocks?
>
> It looks like we get only one try block, so this doesn't have to loop.  But I
> at least added a new test to make sure we warn even with more decls.
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?

OK.

Jason
diff mbox

Patch

diff --git gcc/gimplify.c gcc/gimplify.c
index 8316bb8..8b7dddc 100644
--- gcc/gimplify.c
+++ gcc/gimplify.c
@@ -1609,10 +1609,17 @@  gimplify_switch_expr (tree *expr_p, gimple_seq *pre_p)
 	  while (gimple_code (seq) == GIMPLE_BIND)
 	    seq = gimple_bind_body (as_a <gbind *> (seq));
 	  gimple *stmt = gimple_seq_first_stmt (seq);
-	  enum gimple_code code = gimple_code (stmt);
-	  if (code != GIMPLE_LABEL && code != GIMPLE_TRY)
+	  if (gimple_code (stmt) == GIMPLE_TRY)
 	    {
-	      if (code == GIMPLE_GOTO
+	      /* A compiler-generated cleanup or a user-written try block.
+		 Try to get the first statement in its try-block, for better
+		 location.  */
+	      if ((seq = gimple_try_eval (stmt)))
+		stmt = gimple_seq_first_stmt (seq);
+	    }
+	  if (gimple_code (stmt) != GIMPLE_LABEL)
+	    {
+	      if (gimple_code (stmt) == GIMPLE_GOTO
 		  && TREE_CODE (gimple_goto_dest (stmt)) == LABEL_DECL
 		  && DECL_ARTIFICIAL (gimple_goto_dest (stmt)))
 		/* Don't warn for compiler-generated gotos.  These occur
diff --git gcc/testsuite/c-c++-common/Wswitch-unreachable-3.c gcc/testsuite/c-c++-common/Wswitch-unreachable-3.c
index e69de29..c53cb10 100644
--- gcc/testsuite/c-c++-common/Wswitch-unreachable-3.c
+++ gcc/testsuite/c-c++-common/Wswitch-unreachable-3.c
@@ -0,0 +1,29 @@ 
+/* { dg-do compile } */
+
+extern void f (int *);
+
+void
+g (int i)
+{
+  switch (i)
+    {
+      int a[3];
+      __builtin_memset (a, 0, sizeof a); /* { dg-warning "statement will never be executed" } */
+
+    default:
+      f (a);
+    }
+
+  switch (i)
+    {
+      int a[3];
+      int b[3];
+      int c[3];
+      b[1] = 60; /* { dg-warning "statement will never be executed" } */
+
+    default:
+      f (a);
+      f (b);
+      f (c);
+    }
+}
diff --git gcc/testsuite/g++.dg/warn/Wswitch-unreachable-1.C gcc/testsuite/g++.dg/warn/Wswitch-unreachable-1.C
index e69de29..99d9a83 100644
--- gcc/testsuite/g++.dg/warn/Wswitch-unreachable-1.C
+++ gcc/testsuite/g++.dg/warn/Wswitch-unreachable-1.C
@@ -0,0 +1,34 @@ 
+// { dg-do compile }
+
+extern int j;
+
+void
+f (int i)
+{
+  switch (i) // { dg-warning "statement will never be executed" }
+    {
+      try
+      {
+      }
+      catch (...)
+      {
+      }
+    case 1:;
+    }
+}
+
+void
+g (int i)
+{
+  switch (i)
+    {
+      try
+      {
+	j = 42;  // { dg-warning "statement will never be executed" }
+      }
+      catch (...)
+      {
+      }
+    case 1:;
+    }
+}