diff options
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/cp/parser.c | 28 | ||||
| -rw-r--r-- | gcc/doc/invoke.texi | 18 | ||||
| -rw-r--r-- | gcc/testsuite/g++.dg/warn/Wrange-loop-construct2.C | 212 |
3 files changed, 254 insertions, 4 deletions
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c index cea7cb0..8802124 100644 --- a/gcc/cp/parser.c +++ b/gcc/cp/parser.c @@ -12679,8 +12679,15 @@ do_range_for_auto_deduction (tree decl, tree range_expr) for (const auto &x : range) - if this version doesn't make a copy. DECL is the RANGE_DECL; EXPR is the - *__for_begin expression. + if this version doesn't make a copy. + + This function also warns when the loop variable is initialized with + a value of a different type resulting in a copy: + + int arr[10]; + for (const double &x : arr) + + DECL is the RANGE_DECL; EXPR is the *__for_begin expression. This function is never called when processing_template_decl is on. */ static void @@ -12698,7 +12705,22 @@ warn_for_range_copy (tree decl, tree expr) if (TYPE_REF_P (type)) { - /* TODO: Implement reference warnings. */ + if (glvalue_p (expr) && !ref_conv_binds_directly_p (type, expr)) + { + auto_diagnostic_group d; + if (warning_at (loc, OPT_Wrange_loop_construct, + "loop variable %qD of type %qT binds to a temporary " + "constructed from type %qT", decl, type, + TREE_TYPE (expr))) + { + tree ref = cp_build_qualified_type (TREE_TYPE (expr), + TYPE_QUAL_CONST); + ref = cp_build_reference_type (ref, /*rval*/false); + inform (loc, "use non-reference type %qT to make the copy " + "explicit or %qT to prevent copying", + non_reference (type), ref); + } + } return; } else if (!CP_TYPE_CONST_P (type)) diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 02abac3..26372a2 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -3681,7 +3681,23 @@ void fn () @{ @end smallexample It does not warn when the type being copied is a trivially-copyable type whose -size is less than 64 bytes. This warning is enabled by @option{-Wall}. +size is less than 64 bytes. + +This warning also warns when a loop variable in a range-based for-loop is +initialized with a value of a different type resulting in a copy. For example: + +@smallexample +void fn() @{ + int arr[10]; + for (const double &x : arr) @{ @dots{} @} +@} +@end smallexample + +In the example above, in every iteration of the loop a temporary value of +type @code{double} is created and destroyed, to which the reference +@code{const double &} is bound. + +This warning is enabled by @option{-Wall}. @item -Wredundant-tags @r{(C++ and Objective-C++ only)} @opindex Wredundant-tags diff --git a/gcc/testsuite/g++.dg/warn/Wrange-loop-construct2.C b/gcc/testsuite/g++.dg/warn/Wrange-loop-construct2.C new file mode 100644 index 0000000..5bb08cc --- /dev/null +++ b/gcc/testsuite/g++.dg/warn/Wrange-loop-construct2.C @@ -0,0 +1,212 @@ +// PR c++/94695 +// { dg-do compile { target c++11 } } +// { dg-options "-Wrange-loop-construct" } + +struct Foo { }; +struct Bar { + char arr[100]; + Bar(Foo); + Bar(int); + operator int(); +}; + +template<typename T> +struct It { + T operator*(); + It operator++(); + bool operator!=(const It); +}; + +template<typename T> +struct Cont { + using I = It<T>; + I begin(); + I end(); +}; + +void +fn1 () +{ + int arr[10]; + Cont<int> cont_int; + + for (const double &x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const double x : arr) { (void) x; } + for (const int &x : arr) { (void) x; } + for (double &&x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (double x : arr) { (void) x; } + + for (const int &&x : cont_int) { (void) x; } + for (const int &x : cont_int) { (void) x; } + for (const int x : cont_int) { (void) x; } + for (int&& x : cont_int) { (void) x; } + for (int x : cont_int) { (void) x; } + + for (const double &&x : cont_int) { (void) x; } + for (const double &x : cont_int) { (void) x; } + for (const double x : cont_int) { (void) x; } + + for (double &&x : cont_int) { (void) x; } + for (double x : cont_int) { (void) x; } + + for (const Bar &&x : cont_int) { (void) x; } + for (const Bar x : cont_int) { (void) x; } +} + +void +fn2 () +{ + Cont<int &> cont_int_ref; + + for (const int &x : cont_int_ref) { (void) x; } + for (const int x : cont_int_ref) { (void) x; } + for (int &x : cont_int_ref) { (void) x; } + for (int x : cont_int_ref) { (void) x; } + + for (const double &&x : cont_int_ref) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const double &x : cont_int_ref) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const double x : cont_int_ref) { (void) x; } + for (double &&x : cont_int_ref) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (double x : cont_int_ref) { (void) x; } + + for (const Bar &&x : cont_int_ref) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const Bar &x : cont_int_ref) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const Bar x : cont_int_ref) { (void) x; } + for (Bar &&x : cont_int_ref) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (Bar x : cont_int_ref) { (void) x; } +} + +void +fn3 () +{ + Cont<Bar> cont_bar; + + for (const Bar &&x : cont_bar) { (void) x; } + for (const Bar &x : cont_bar) { (void) x; } + for (const Bar x : cont_bar) { (void) x; } + for (Bar &&x : cont_bar) { (void) x; } + for (Bar x : cont_bar) { (void) x; } + + for (const int &&x : cont_bar) { (void) x; } + for (const int &x : cont_bar) { (void) x; } + for (const int x : cont_bar) { (void) x; } + for (int &&x : cont_bar) { (void) x; } + for (int x : cont_bar) { (void) x; } +} + +void +fn4 () +{ + Cont<Bar &> cont_bar_ref; + + for (const Bar &x : cont_bar_ref) { (void) x; } + for (Bar &x : cont_bar_ref) { (void) x; } + for (Bar x : cont_bar_ref) { (void) x; } + + for (const int &&x : cont_bar_ref) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const int &x : cont_bar_ref) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const int x : cont_bar_ref) { (void) x; } + for (int &&x : cont_bar_ref) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (int x : cont_bar_ref) { (void) x; } +} + +void +fn5 () +{ + Cont<Foo> cont_foo; + + for (const Bar &&x : cont_foo) { (void) x; } + for (const Bar &x : cont_foo) { (void) x; } + for (const Bar x : cont_foo) { (void) x; } + for (Bar &&x : cont_foo) { (void) x; } + for (Bar x : cont_foo) { (void) x; } +} + +void +fn6 () +{ + Cont<Foo &> cont_foo_ref; + + for (const Bar &&x : cont_foo_ref) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const Bar &x : cont_foo_ref) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const Bar x : cont_foo_ref) { (void) x; } + for (Bar &&x : cont_foo_ref) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (Bar x : cont_foo_ref) { (void) x; } +} + +void +fn7 () +{ + double arr[2]; + + for (const double &x : arr) { (void) x; } + for (const double x : arr) { (void) x; } + for (double &x : arr) { (void) x; } + for (double x : arr) { (void) x; } + + for (const int &&x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const int &x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const int x : arr) { (void) x; } + for (int &&x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (int x : arr) { (void) x; } + + for (const Bar &&x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const Bar &x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const Bar x : arr) { (void) x; } + for (Bar &&x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (Bar x : arr) { (void) x; } +} + +void +fn8 () +{ + Foo arr[2]; + + for (const Foo &x : arr) { (void) x; } + for (const Foo x : arr) { (void) x; } + for (Foo &x : arr) { (void) x; } + for (Foo x : arr) { (void) x; } + + for (const Bar &&x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const Bar &x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const Bar x : arr) { (void) x; } + for (Bar &&x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (Bar x : arr) { (void) x; } +} + +void +fn9 () +{ + Bar arr[2] = { 1, 2 }; + + for (const Bar &x : arr) { (void) x; } + for (Bar &x : arr) { (void) x; } + for (Bar x : arr) { (void) x; } + + for (const int &&x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const int &x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (const int x : arr) { (void) x; } + for (int &&x : arr) { (void) x; } // { dg-warning "binds to a temporary constructed from type" } + for (int x : arr) { (void) x; } +} + +template<typename T> +void +fn10 () +{ + Cont<Bar> cont_bar; + + for (const Bar &x : cont_bar) { (void) x; } + + Cont<T> cont_dep; + for (const T &x : cont_dep) { (void) x; } +} +template void fn10<Bar>(); + +struct S { + void fn() + { + Cont<Bar> cont_bar; + for (const Bar &x : cont_bar) { (void) x; } + } +}; |