Re: Further refinement to -Wswitch-unreachable

[Jason Merrill]

On Tue, May 31, 2016 at 9:40 AM, Marek Polacek  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

Re: Further refinement to -Wswitch-unreachable

[Marek Polacek]

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  

* 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.

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  (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:;
+}
+}

Marek

Re: Further refinement to -Wswitch-unreachable

[Jason Merrill]

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?


Jason

Further refinement to -Wswitch-unreachable

[Marek Polacek]

Martin complained that -Wswitch-unreachable wouldn't warn on try-blocks,
either compiler-generated or user-written.  This patch, which looks into
GIMPLE_TRY's body, seems to DTRT for both.

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

2016-05-26  Marek Polacek  

* 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.

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  (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..3748701 100644
--- gcc/testsuite/c-c++-common/Wswitch-unreachable-3.c
+++ gcc/testsuite/c-c++-common/Wswitch-unreachable-3.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+
+extern void f (int *, 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, 3);
+}
+}
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:;
+}
+}

Marek