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); + if (!usings) + return false; + + for (unsigned ix = usings->length (); ix--;) + if ((*usings)[ix] == std_node) + return true; + + 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 @@ -5397,11 +5415,23 @@ 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); @@ -5509,20 +5539,13 @@ 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); @@ -5539,6 +5562,23 @@ 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..95946ff --- /dev/null +++ b/gcc/testsuite/g++.dg/lookup/missing-std-include-7.C @@ -0,0 +1,16 @@ +/* PR c++/85021: Verify that we suggest missing headers for common names in std:: + if there's a "using namespace std;" active. */ + +void test_without_using_directive () +{ + cout << "test"; // { dg-error "'cout' was not declared in this scope" } + // { dg-bogus "'<iostream>'" "" { target *-*-* } .-1 } +} + +using namespace std; + +void test_with_using_directive () +{ + 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