From: Lubos Lunak Date: Sat, 13 Jul 2013 23:16:18 +0000 (+0200) Subject: re PR c++/55203 (No unused warning for variables of non-trivial types) X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=2a99e5e633fb1faddeb8c8ce7b1429dedebb033b;p=gcc.git re PR c++/55203 (No unused warning for variables of non-trivial types) PR c++/55203 c-family/ * c-common.c (c_common_attribute_table): Add warn_unused. (handle_warn_unused_attribute): New. cp/ * init.c (build_aggr_init): Check for warn_unused attribute. * decl.c (poplevel): Likewise. From-SVN: r200941 --- diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog index 5aeb338b4d5..27b22a19fbd 100644 --- a/gcc/c-family/ChangeLog +++ b/gcc/c-family/ChangeLog @@ -1,3 +1,9 @@ +2013-07-13 Lubos Lunak + + PR c++/55203 + * c-common.c (c_common_attribute_table): Add warn_unused. + (handle_warn_unused_attribute): New. + 2013-07-10 Jakub Jelinek * c-ppoutput.c (scan_translation_unit): Call account_for_newlines diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c index 61300cd05c7..970f9f20a08 100644 --- a/gcc/c-family/c-common.c +++ b/gcc/c-family/c-common.c @@ -368,6 +368,7 @@ static tree handle_optimize_attribute (tree *, tree, tree, int, bool *); static tree ignore_attribute (tree *, tree, tree, int, bool *); static tree handle_no_split_stack_attribute (tree *, tree, tree, int, bool *); static tree handle_fnspec_attribute (tree *, tree, tree, int, bool *); +static tree handle_warn_unused_attribute (tree *, tree, tree, int, bool *); static void check_function_nonnull (tree, int, tree *); static void check_nonnull_arg (void *, tree, unsigned HOST_WIDE_INT); @@ -738,6 +739,8 @@ const struct attribute_spec c_common_attribute_table[] = The name contains space to prevent its usage in source code. */ { "fn spec", 1, 1, false, true, true, handle_fnspec_attribute, false }, + { "warn_unused", 0, 0, false, false, false, + handle_warn_unused_attribute, false }, { NULL, 0, 0, false, false, false, NULL, false } }; @@ -7950,6 +7953,27 @@ handle_fnspec_attribute (tree *node ATTRIBUTE_UNUSED, tree ARG_UNUSED (name), return NULL_TREE; } +/* Handle a "warn_unused" attribute; arguments as in + struct attribute_spec.handler. */ + +static tree +handle_warn_unused_attribute (tree *node, tree name, + tree args ATTRIBUTE_UNUSED, + int flags ATTRIBUTE_UNUSED, bool *no_add_attrs) +{ + if (TYPE_P (*node)) + /* Do nothing else, just set the attribute. We'll get at + it later with lookup_attribute. */ + ; + else + { + warning (OPT_Wattributes, "%qE attribute ignored", name); + *no_add_attrs = true; + } + + return NULL_TREE; +} + /* Handle a "returns_twice" attribute; arguments as in struct attribute_spec.handler. */ diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index 4e466305829..3cf5e779791 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,9 @@ +2013-07-13 Lubos Lunak + + PR c++/55203 + * init.c (build_aggr_init): Check for warn_unused attribute. + * decl.c (poplevel): Likewise. + 2013-07-13 Jason Merrill PR c++/57402 diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c index 54bede00bb1..c97134c5c40 100644 --- a/gcc/cp/decl.c +++ b/gcc/cp/decl.c @@ -630,7 +630,9 @@ poplevel (int keep, int reverse, int functionbody) && DECL_NAME (decl) && ! DECL_ARTIFICIAL (decl) && type != error_mark_node && (!CLASS_TYPE_P (type) - || !TYPE_HAS_NONTRIVIAL_DESTRUCTOR (type))) + || !TYPE_HAS_NONTRIVIAL_DESTRUCTOR (type) + || lookup_attribute ("warn_unused", + TYPE_ATTRIBUTES (TREE_TYPE (decl))))) { if (! TREE_USED (decl)) warning (OPT_Wunused_variable, "unused variable %q+D", decl); diff --git a/gcc/cp/init.c b/gcc/cp/init.c index 808803d6524..3bff509b396 100644 --- a/gcc/cp/init.c +++ b/gcc/cp/init.c @@ -1504,7 +1504,8 @@ build_aggr_init (tree exp, tree init, int flags, tsubst_flags_t complain) return stmt_expr; } - if (VAR_P (exp) || TREE_CODE (exp) == PARM_DECL) + if ((VAR_P (exp) || TREE_CODE (exp) == PARM_DECL) + && !lookup_attribute ("warn_unused", TYPE_ATTRIBUTES (type))) /* Just know that we've seen something for this node. */ TREE_USED (exp) = 1; diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index 1c85a3e7382..721c9b10daf 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -16377,6 +16377,23 @@ only be applied to classes declared within an @code{extern "Java"} block. Calls to methods declared in this interface are dispatched using GCJ's interface table mechanism, instead of regular virtual table dispatch. +@item warn_unused +@cindex @code{warn_unused} attribute + +For C++ types with non-trivial constructors and/or destructors it is +impossible for the compiler to determine whether a variable of this +type is truly unused if it is not referenced. This type attribute +informs the compiler that variables of this type should be warned +about if they appear to be unused, just like variables of fundamental +types. + +This attribute is appropriate for types which just represent a value, +such as @code{std::string}; it is not appropriate for types which +control a resource, such as @code{std::mutex}. + +This attribute is also accepted in C, but it is unnecessary because C +does not have constructors or destructors. + @end table See also @ref{Namespace Association}. diff --git a/gcc/testsuite/g++.dg/warn/warn_unused.C b/gcc/testsuite/g++.dg/warn/warn_unused.C new file mode 100644 index 00000000000..af687fc1671 --- /dev/null +++ b/gcc/testsuite/g++.dg/warn/warn_unused.C @@ -0,0 +1,22 @@ +// { dg-do compile } +// { dg-options -Wunused } + +struct __attribute__((warn_unused)) Test +{ + Test(); + ~Test(); + void use(); +}; + +struct TestNormal +{ + TestNormal(); +}; + +int main() +{ + Test unused; // { dg-warning "unused variable" } + Test used; // { dg-bogus "unused variable" } + TestNormal normal; // { dg-bogus "unused variable" } + used.use(); +}