From cb731872870ff15c4d4a4dc081191ed607faaa2b Mon Sep 17 00:00:00 2001 From: David Malcolm Date: Fri, 6 Apr 2018 15:46:04 +0000 Subject: [PATCH] C++: suggest missing headers for implicit use of "std" (PR c++/85021) 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 ''; did you forget to '#include '? +#include using namespace std; void f() { cout << "test"; } ^~~~ 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. From-SVN: r259179 --- gcc/cp/ChangeLog | 13 +++ gcc/cp/name-lookup.c | 93 +++++++++++++--- gcc/testsuite/ChangeLog | 5 + .../g++.dg/lookup/missing-std-include-7.C | 100 ++++++++++++++++++ 4 files changed, 197 insertions(+), 14 deletions(-) create mode 100644 gcc/testsuite/g++.dg/lookup/missing-std-include-7.C diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index 71a5d45c194..a27484b5e18 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,16 @@ +2018-04-06 David Malcolm + + 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. + 2018-04-06 Jason Merrill PR c++/85242 - ICE with class definition in template parm. diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c index 62f0b3f037b..dc7699d5366 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 *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/ChangeLog b/gcc/testsuite/ChangeLog index 0ea9f647517..e192061962e 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2018-04-06 David Malcolm + + PR c++/85021 + * g++.dg/lookup/missing-std-include-7.C: New test. + 2018-04-06 Tamar Christina * gcc.dg/struct-simple.c: Revert r254862. 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 00000000000..4c87c8c0c4f --- /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 "''" "" { 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 ''" "" { 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 "''" "" { 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 "''" "" { 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 ''" "" { 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 ''" "" { 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 ''" "" { 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 "''" "" { 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 ''" "" { target *-*-* } .-1 } +} + -- 2.30.2