From: Mark Wielaard Date: Mon, 14 Sep 2015 09:49:47 +0000 (+0000) Subject: PR28901 -Wunused-variable ignores unused const initialised variables in C X-Git-Tag: basepoints/gcc-7~4591 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=0f876f22887f239cedca64ff170b71e5f1daaf54;p=thirdparty%2Fgcc.git PR28901 -Wunused-variable ignores unused const initialised variables in C 12 years ago it was decided that -Wunused-variable shouldn't warn about static const variables because some code used const static char rcsid[] strings which were never used but wanted in the code anyway. But as the bug points out this hides some real bugs. These days the usage of rcsids is not very popular anymore. So this patch changes the default to warn about unused static const variables in C with -Wunused-variable. And it adds a new option -Wno-unused-const-variable to turn this warning off. For C++ this new warning is off by default, since const variables can be used as #defines in C++. New testcases for the new defaults in C and C++ are included testing the new warning and suppressing it with an unused attribute or using -Wno-unused-const-variable. gcc/ChangeLog PR c/28901 * toplev.c (check_global_declaration): Check and use warn_unused_const_variable. * doc/invoke.texi (Warning Options): Add -Wunused-const-variable. (-Wunused-variable): Remove non-constant. For C implies -Wunused-const-variable. (-Wunused-const-variable): New. gcc/c-family/ChangeLog PR c/28901 * c.opt (Wunused-variable): Option from common.opt. (Wunused-const-variable): New option. gcc/cp/ChangeLog PR c/28901 * cp-objcp-common.c (cxx_warn_unused_global_decl): Remove hard-coded VAR_P TREE_READONLY override. gcc/testsuite/ChangeLog PR c/28901 * g++.dg/warn/unused-variable-1.C: New test. * g++.dg/warn/unused-variable-2.C: Likewise. * gcc.dg/unused-4.c: Adjust warning for static const. * gcc.dg/unused-variable-1.c: New test. * gcc.dg/unused-variable-2.c: Likewise. From-SVN: r227742 --- diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 9059ffa23e88..0aa46d051506 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,13 @@ +2015-09-11 Mark Wielaard + + PR c/28901 + * toplev.c (check_global_declaration): Check and use + warn_unused_const_variable. + * doc/invoke.texi (Warning Options): Add -Wunused-const-variable. + (-Wunused-variable): Remove non-constant. For C implies + -Wunused-const-variable. + (-Wunused-const-variable): New. + 2015-09-14 Richard Biener * doc/match-and-simplify.texi: Update for changed syntax diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog index 3acc84f433b3..0163b1593dd6 100644 --- a/gcc/c-family/ChangeLog +++ b/gcc/c-family/ChangeLog @@ -1,3 +1,9 @@ +2015-09-11 Mark Wielaard + + PR c/28901 + * c.opt (Wunused-variable): Option from common.opt. + (Wunused-const-variable): New option. + 2015-09-09 Paolo Carlini PR c++/53184 diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt index d519d7a000bf..47ba0704da8d 100644 --- a/gcc/c-family/c.opt +++ b/gcc/c-family/c.opt @@ -912,6 +912,14 @@ Wunused-result C ObjC C++ ObjC++ Var(warn_unused_result) Init(1) Warning Warn if a caller of a function, marked with attribute warn_unused_result, does not use its return value +Wunused-variable +C ObjC C++ ObjC++ LangEnabledBy(C ObjC C++ ObjC++,Wunused) +; documented in common.opt + +Wunused-const-variable +C ObjC C++ ObjC++ Var(warn_unused_const_variable) Warning LangEnabledBy(C ObjC,Wunused-variable) +Warn when a const variable is unused + Wvariadic-macros C ObjC C++ ObjC++ CPP(warn_variadic_macros) CppReason(CPP_W_VARIADIC_MACROS) Var(cpp_warn_variadic_macros) Init(0) Warning LangEnabledBy(C ObjC C++ ObjC++,Wpedantic || Wtraditional) Warn about using variadic macros diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index a9952fcae755..4101a2e123ef 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,9 @@ +2015-09-11 Mark Wielaard + + PR c/28901 + * cp-objcp-common.c (cxx_warn_unused_global_decl): Remove hard-coded + VAR_P TREE_READONLY override. + 2015-09-10 Paolo Carlini PR c++/67318 diff --git a/gcc/cp/cp-objcp-common.c b/gcc/cp/cp-objcp-common.c index 2cab89c1552d..808defdb986f 100644 --- a/gcc/cp/cp-objcp-common.c +++ b/gcc/cp/cp-objcp-common.c @@ -62,10 +62,6 @@ cxx_warn_unused_global_decl (const_tree decl) if (DECL_IN_SYSTEM_HEADER (decl)) return false; - /* Const variables take the place of #defines in C++. */ - if (VAR_P (decl) && TREE_READONLY (decl)) - return false; - return true; } diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 518d68933c9f..7b5e44e08810 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -290,6 +290,7 @@ Objective-C and Objective-C++ Dialects}. -Wunsuffixed-float-constants -Wunused -Wunused-function @gol -Wunused-label -Wunused-local-typedefs -Wunused-parameter @gol -Wno-unused-result -Wunused-value @gol -Wunused-variable @gol +-Wunused-const-variable @gol -Wunused-but-set-parameter -Wunused-but-set-variable @gol -Wuseless-cast -Wvariadic-macros -Wvector-operation-performance @gol -Wvla -Wvolatile-register-var -Wwrite-strings @gol @@ -4143,9 +4144,20 @@ its return value. The default is @option{-Wunused-result}. @item -Wunused-variable @opindex Wunused-variable @opindex Wno-unused-variable -Warn whenever a local variable or non-constant static variable is unused -aside from its declaration. -This warning is enabled by @option{-Wall}. +Warn whenever a local or static variable is unused aside from its +declaration. This option implies @option{-Wunused-const-variable} for C, +but not for C++. This warning is enabled by @option{-Wall}. + +To suppress this warning use the @code{unused} attribute +(@pxref{Variable Attributes}). + +@item -Wunused-const-variable +@opindex Wunused-const-variable +@opindex Wno-unused-const-variable +Warn whenever a constant static variable is unused aside from its declaration. +This warning is enabled by @option{-Wunused-variable} for C, but not for C++. +In C++ this is normally not an error since const variables take the place of +@code{#define}s in C++. To suppress this warning use the @code{unused} attribute (@pxref{Variable Attributes}). diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 65dde8ccc7be..a285ee22b903 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,12 @@ +2015-09-11 Mark Wielaard + + PR c/28901 + * g++.dg/warn/unused-variable-1.C: New test. + * g++.dg/warn/unused-variable-2.C: Likewise. + * gcc.dg/unused-4.c: Adjust warning for static const. + * gcc.dg/unused-variable-1.c: New test. + * gcc.dg/unused-variable-2.c: Likewise. + 2015-09-13 David Edelsohn * gfortran.dg/private_type_3.f90: Require visibility. diff --git a/gcc/testsuite/g++.dg/warn/unused-variable-1.C b/gcc/testsuite/g++.dg/warn/unused-variable-1.C new file mode 100644 index 000000000000..cf531c01f18e --- /dev/null +++ b/gcc/testsuite/g++.dg/warn/unused-variable-1.C @@ -0,0 +1,7 @@ +/* { dg-do compile } */ +/* { dg-options "-Wunused-variable" } */ + +static int a = 0; /* { dg-warning "defined but not used" } */ +static const int b = 0; /* Unlike C, this doesn't cause a warning in C++. */ +static int c __attribute__ ((unused)) = 0; +static const char rcsid[] = "version-string"; /* Likewise. */ diff --git a/gcc/testsuite/g++.dg/warn/unused-variable-2.C b/gcc/testsuite/g++.dg/warn/unused-variable-2.C new file mode 100644 index 000000000000..b608fbce038f --- /dev/null +++ b/gcc/testsuite/g++.dg/warn/unused-variable-2.C @@ -0,0 +1,7 @@ +/* { dg-do compile } */ +/* { dg-options "-Wunused-variable -Wunused-const-variable" } */ + +static int a = 0; /* { dg-warning "defined but not used" } */ +static const int b = 0; /* { dg-warning "defined but not used" } */ +static int c __attribute__ ((unused)) = 0; +static const char rcsid[] __attribute__ ((unused)) = "version-string"; diff --git a/gcc/testsuite/gcc.dg/unused-4.c b/gcc/testsuite/gcc.dg/unused-4.c index 99e845f45a3c..53236008007a 100644 --- a/gcc/testsuite/gcc.dg/unused-4.c +++ b/gcc/testsuite/gcc.dg/unused-4.c @@ -1,6 +1,6 @@ /* { dg-do compile } */ /* { dg-options "-Wunused -O3" } */ -static const int i = 0; +static const int i = 0; /* { dg-warning "defined but not used" } */ static void f() { } /* { dg-warning "defined but not used" } */ static inline void g() { } diff --git a/gcc/testsuite/gcc.dg/unused-variable-1.c b/gcc/testsuite/gcc.dg/unused-variable-1.c new file mode 100644 index 000000000000..cb86c3bc8d26 --- /dev/null +++ b/gcc/testsuite/gcc.dg/unused-variable-1.c @@ -0,0 +1,7 @@ +/* { dg-do compile } */ +/* { dg-options "-Wunused-variable" } */ + +static int a = 0; /* { dg-warning "defined but not used" } */ +static const int b = 0; /* { dg-warning "defined but not used" } */ +static int c __attribute__ ((unused)) = 0; +static const char rcsid[] __attribute__ ((unused)) = "version-string"; diff --git a/gcc/testsuite/gcc.dg/unused-variable-2.c b/gcc/testsuite/gcc.dg/unused-variable-2.c new file mode 100644 index 000000000000..0496466a45f0 --- /dev/null +++ b/gcc/testsuite/gcc.dg/unused-variable-2.c @@ -0,0 +1,7 @@ +/* { dg-do compile } */ +/* { dg-options "-Wunused-variable -Wno-unused-const-variable" } */ + +static int a = 0; /* { dg-warning "defined but not used" } */ +static const int b = 0; +static int c __attribute__ ((unused)) = 0; +static const char rcsid[] = "version-string"; diff --git a/gcc/toplev.c b/gcc/toplev.c index 926224a4c204..95e4c522e4a5 100644 --- a/gcc/toplev.c +++ b/gcc/toplev.c @@ -497,10 +497,9 @@ check_global_declaration (tree decl) /* Warn about static fns or vars defined but not used. */ if (((warn_unused_function && TREE_CODE (decl) == FUNCTION_DECL) - /* We don't warn about "static const" variables because the - "rcs_id" idiom uses that construction. */ - || (warn_unused_variable - && TREE_CODE (decl) == VAR_DECL && ! TREE_READONLY (decl))) + || (((warn_unused_variable && ! TREE_READONLY (decl)) + || (warn_unused_const_variable && TREE_READONLY (decl))) + && TREE_CODE (decl) == VAR_DECL)) && ! DECL_IN_SYSTEM_HEADER (decl) && ! snode->referred_to_p (/*include_self=*/false) /* This TREE_USED check is needed in addition to referred_to_p @@ -527,7 +526,9 @@ check_global_declaration (tree decl) warning_at (DECL_SOURCE_LOCATION (decl), (TREE_CODE (decl) == FUNCTION_DECL) ? OPT_Wunused_function - : OPT_Wunused_variable, + : (TREE_READONLY (decl) + ? OPT_Wunused_const_variable + : OPT_Wunused_variable), "%qD defined but not used", decl); }