On Thu, 2018-03-29 at 15:25 -0400, Jason Merrill wrote:
> On Thu, Mar 22, 2018 at 7:44 PM, David Malcolm <dmalc...@redhat.com>
> wrote:
> > We provide fix-it hints for the most common "std" names when an
> > explicit
> > "std::" prefix is present, however we don't yet provide fix-it
> > hints for
> > this implicit case:
> >
> > using namespace std;
> > void f() { cout << "test"; }
> >
> > for which we emit:
> >
> > t.cc: In function 'void f()':
> > t.cc:2:13: error: 'cout' was not declared in this scope
> > void f() { cout << "test"; }
> > ^~~~
> >
> > This patch detects if a "using namespace std;" directive is present
> > in the current namespace, and if so, offers a suggestion for
> > unrecognized names that are in our list of common "std" names:
> >
> > t.cc: In function 'void f()':
> > t.cc:2:13: error: 'cout' was not declared in this scope
> > void f() { cout << "test"; }
> > ^~~~
> > t.cc:2:13: note: 'std::cout' is defined in header '<iostream>';
> > did you forget to '#include <iostream>'?
> > +#include <iostream>
> > using namespace std;
> > void f() { cout << "test"; }
> > ^~~~
> >
> > Is there a better way to test for the using directive?
> >
> > Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
> >
> > OK for trunk?
> >
> > gcc/cp/ChangeLog:
> > PR c++/85021
> > * name-lookup.c (has_using_namespace_std_directive_p): New
> > function.
> > (suggest_alternatives_for): Simplify if/else logic using
> > early
> > returns. If no candidates were found, and there's a
> > "using namespace std;" directive, call
> > maybe_suggest_missing_std_header.
> > (maybe_suggest_missing_header): Split later part of the
> > function
> > into..
> > (maybe_suggest_missing_std_header): New.
> >
> > gcc/testsuite/ChangeLog:
> > PR c++/85021
> > * g++.dg/lookup/missing-std-include-7.C: New test.
> > ---
> > gcc/cp/name-lookup.c | 68
> > +++++++++++++++++-----
> > .../g++.dg/lookup/missing-std-include-7.C | 16 +++++
> > 2 files changed, 70 insertions(+), 14 deletions(-)
> > create mode 100644 gcc/testsuite/g++.dg/lookup/missing-std-
> > include-7.C
> >
> > diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
> > index 061729a..4eb980e 100644
> > --- a/gcc/cp/name-lookup.c
> > +++ b/gcc/cp/name-lookup.c
> > @@ -41,6 +41,7 @@ static cxx_binding *cxx_binding_make (tree value,
> > tree type);
> > static cp_binding_level *innermost_nonclass_level (void);
> > static void set_identifier_type_value_with_scope (tree id, tree
> > decl,
> > cp_binding_level
> > *b);
> > +static bool maybe_suggest_missing_std_header (location_t location,
> > tree name);
> >
> > /* Create an overload suitable for recording an artificial
> > TYPE_DECL
> > and another decl. We use this machanism to implement the
> > struct
> > @@ -5327,6 +5328,23 @@ qualify_lookup (tree val, int flags)
> > return true;
> > }
> >
> > +/* Is there a "using namespace std;" directive within the current
> > + namespace? */
> > +
> > +static bool
> > +has_using_namespace_std_directive_p ()
> > +{
> > + vec<tree, va_gc> *usings = DECL_NAMESPACE_USING
> > (current_namespace);
>
> Checking in just the current namespace won't find a "using namespace
> std" in an inner or outer scope; I think you want to add something to
> name-lookup.c that iterates over the current enclosing scopes like
> name_lookup::search_unqualified. Nathan can probably be more
> specific.
>
> Jason
Thanks.
Here's an updated version of the patch.
Rather than just search in DECL_NAMESPACE_USING (current_namespace),
this version mimics name_lookup::search_unqualified by searching for local
using-directives in the current_binding_level until it reaches a sk_namespace,
and then searching in current_namespace and its ancestors.
(and builds out the test coverage accordingly)
Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu; adds
57 PASS results to g++.sum.
OK for trunk?
gcc/cp/ChangeLog:
PR c++/85021
* name-lookup.c (using_directives_contain_std_p): New function.
(has_using_namespace_std_directive_p): New function.
(suggest_alternatives_for): Simplify if/else logic using early
returns. If no candidates were found, and there's a
"using namespace std;" directive, call
maybe_suggest_missing_std_header.
(maybe_suggest_missing_header): Split later part of the function
into..
(maybe_suggest_missing_std_header): New.
gcc/testsuite/ChangeLog:
PR c++/85021
* g++.dg/lookup/missing-std-include-7.C: New test.
---
gcc/cp/name-lookup.c | 93 ++++++++++++++++---
.../g++.dg/lookup/missing-std-include-7.C | 100 +++++++++++++++++++++
2 files changed, 179 insertions(+), 14 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/lookup/missing-std-include-7.C
diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 9b5db3d..a9f3094 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -41,6 +41,7 @@ static cxx_binding *cxx_binding_make (tree value, tree type);
static cp_binding_level *innermost_nonclass_level (void);
static void set_identifier_type_value_with_scope (tree id, tree decl,
cp_binding_level *b);
+static bool maybe_suggest_missing_std_header (location_t location, tree name);
/* Create an overload suitable for recording an artificial TYPE_DECL
and another decl. We use this machanism to implement the struct
@@ -5330,6 +5331,48 @@ qualify_lookup (tree val, int flags)
return true;
}
+/* Is there a "using namespace std;" directive within USINGS? */
+
+static bool
+using_directives_contain_std_p (vec<tree, va_gc> *usings)
+{
+ if (!usings)
+ return false;
+
+ for (unsigned ix = usings->length (); ix--;)
+ if ((*usings)[ix] == std_node)
+ return true;
+
+ return false;
+}
+
+/* Is there a "using namespace std;" directive within the current
+ namespace (or its ancestors)?
+ Compare with name_lookup::search_unqualified. */
+
+static bool
+has_using_namespace_std_directive_p ()
+{
+ /* Look at local using-directives. */
+ for (cp_binding_level *level = current_binding_level;
+ level->kind != sk_namespace;
+ level = level->level_chain)
+ if (using_directives_contain_std_p (level->using_directives))
+ return true;
+
+ /* Look at this namespace and its ancestors. */
+ for (tree scope = current_namespace; scope; scope = CP_DECL_CONTEXT (scope))
+ {
+ if (using_directives_contain_std_p (DECL_NAMESPACE_USING (scope)))
+ return true;
+
+ if (scope == global_namespace)
+ break;
+ }
+
+ return false;
+}
+
/* Suggest alternatives for NAME, an IDENTIFIER_NODE for which name
lookup failed. Search through all available namespaces and print out
possible candidates. If no exact matches are found, and
@@ -5400,11 +5443,23 @@ suggest_alternatives_for (location_t location, tree
name,
inform (location_of (val), " %qE", val);
}
candidates.release ();
+ return;
}
- else if (!suggest_misspellings)
- ;
- else if (name_hint hint = lookup_name_fuzzy (name, FUZZY_LOOKUP_NAME,
- location))
+
+ /* No candidates were found in the available namespaces. */
+
+ /* If there's a "using namespace std;" active, and this
+ is one of the most common "std::" names, then it's probably a
+ missing #include. */
+ if (has_using_namespace_std_directive_p ())
+ if (maybe_suggest_missing_std_header (location, name))
+ return;
+
+ /* Otherwise, consider misspellings. */
+ if (!suggest_misspellings)
+ return;
+ if (name_hint hint = lookup_name_fuzzy (name, FUZZY_LOOKUP_NAME,
+ location))
{
/* Show a spelling correction. */
gcc_rich_location richloc (location);
@@ -5512,20 +5567,13 @@ get_std_name_hint (const char *name)
return NULL;
}
-/* If SCOPE is the "std" namespace, then suggest pertinent header
- files for NAME at LOCATION.
+/* Suggest pertinent header files for NAME at LOCATION, for common
+ names within the "std" namespace.
Return true iff a suggestion was offered. */
static bool
-maybe_suggest_missing_header (location_t location, tree name, tree scope)
+maybe_suggest_missing_std_header (location_t location, tree name)
{
- if (scope == NULL_TREE)
- return false;
- if (TREE_CODE (scope) != NAMESPACE_DECL)
- return false;
- /* We only offer suggestions for the "std" namespace. */
- if (scope != std_node)
- return false;
gcc_assert (TREE_CODE (name) == IDENTIFIER_NODE);
const char *name_str = IDENTIFIER_POINTER (name);
@@ -5542,6 +5590,23 @@ maybe_suggest_missing_header (location_t location, tree
name, tree scope)
return true;
}
+/* If SCOPE is the "std" namespace, then suggest pertinent header
+ files for NAME at LOCATION.
+ Return true iff a suggestion was offered. */
+
+static bool
+maybe_suggest_missing_header (location_t location, tree name, tree scope)
+{
+ if (scope == NULL_TREE)
+ return false;
+ if (TREE_CODE (scope) != NAMESPACE_DECL)
+ return false;
+ /* We only offer suggestions for the "std" namespace. */
+ if (scope != std_node)
+ return false;
+ return maybe_suggest_missing_std_header (location, name);
+}
+
/* Look for alternatives for NAME, an IDENTIFIER_NODE for which name
lookup failed within the explicitly provided SCOPE. Suggest the
the best meaningful candidates (if any) as a fix-it hint.
diff --git a/gcc/testsuite/g++.dg/lookup/missing-std-include-7.C
b/gcc/testsuite/g++.dg/lookup/missing-std-include-7.C
new file mode 100644
index 0000000..4c87c8c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/lookup/missing-std-include-7.C
@@ -0,0 +1,100 @@
+/* PR c++/85021: Verify that we suggest missing headers for common names in
std::
+ if there's a "using namespace std;" active. */
+
+/* No using-directive. */
+
+void test_1 ()
+{
+ cout << "test"; // { dg-error "'cout' was not declared in this scope" }
+ // { dg-bogus "'<iostream>'" "" { target *-*-* } .-1 }
+}
+
+/* Local using-directive. */
+
+void test_2 ()
+{
+ using namespace std;
+ cout << "test"; // { dg-error "'cout' was not declared in this scope" }
+ // { dg-message "'std::cout' is defined in header '<iostream>'" "" { target
*-*-* } .-1 }
+}
+
+/* Local using-directive, but not of "std". */
+
+namespace not_std {}
+void test_3 ()
+{
+ using namespace not_std;
+ cout << "test"; // { dg-error "'cout' was not declared in this scope" }
+ // { dg-bogus "'<iostream>'" "" { target *-*-* } .-1 }
+}
+
+/* Local using-directive in wrong block. */
+
+void test_4 ()
+{
+ {
+ using namespace std;
+ }
+ cout << "test"; // { dg-error "'cout' was not declared in this scope" }
+ // { dg-bogus "'<iostream>'" "" { target *-*-* } .-1 }
+}
+
+/* Local using-directive used from nested block. */
+
+void test_5 ()
+{
+ using namespace std;
+
+ for (int i = 0; i < 10; i++)
+ {
+ cout << "test"; // { dg-error "'cout' was not declared in this scope" }
+ // { dg-message "'std::cout' is defined in header '<iostream>'" "" {
target *-*-* } .-1 }
+ }
+}
+
+namespace ns_1 {
+
+namespace ns_2 {
+
+using namespace std;
+
+/* using-directive within the same namespace. */
+
+void test_6 ()
+{
+ cout << "test"; // { dg-error "'cout' was not declared in this scope" }
+ // { dg-message "'std::cout' is defined in header '<iostream>'" "" { target
*-*-* } .-1 }
+}
+
+namespace ns_3 {
+
+/* Locate the using-directive within ns_2, the parent namespace. */
+
+void test_7 ()
+{
+ cout << "test"; // { dg-error "'cout' was not declared in this scope" }
+ // { dg-message "'std::cout' is defined in header '<iostream>'" "" { target
*-*-* } .-1 }
+}
+
+} // namespace ns_3
+} // namespace ns_2
+
+/* Back in ns_1, should not locate the using-directive. */
+
+void test_8 ()
+{
+ cout << "test"; // { dg-error "'cout' was not declared in this scope" }
+ // { dg-bogus "'<iostream>'" "" { target *-*-* } .-1 }
+}
+
+} // namespace ns_1
+
+/* using-directive in global namespace. */
+using namespace std;
+
+void test_9 ()
+{
+ cout << "test"; // { dg-error "'cout' was not declared in this scope" }
+ // { dg-message "'std::cout' is defined in header '<iostream>'" "" { target
*-*-* } .-1 }
+}
+
--
1.8.5.3
