From e0d91792eec490d1bddb4a095a3da2c5b4c270e2 Mon Sep 17 00:00:00 2001 From: Bernd Edlinger Date: Wed, 30 Oct 2019 20:29:21 +0000 Subject: [PATCH] re PR c++/92024 (crash in check_local_shadow) 2019-10-30 Bernd Edlinger * doc/invoke.texi (-Wshadow, -Wshadow=global -Wshadow=local, -Wshadow=compatible-local): Update documentation. cp: 2019-10-30 Bernd Edlinger PR c++/92024 * name-lookup.c (check_local_shadow): Shadowing TYPE_DECLs is always a -Wshadow=compatible-local warning, unless -Wshadow is used. testsuite: 2019-10-30 Bernd Edlinger PR c++/92024 * g++.dg/parse/crash70.C: New test. * c-c++-common/Wshadow-1.c: New test. From-SVN: r277643 --- gcc/ChangeLog | 5 ++++ gcc/cp/ChangeLog | 7 +++++ gcc/cp/name-lookup.c | 36 ++++++++++++++------------ gcc/doc/invoke.texi | 32 ++++++++++++----------- gcc/testsuite/ChangeLog | 6 +++++ gcc/testsuite/c-c++-common/Wshadow-1.c | 24 +++++++++++++++++ gcc/testsuite/g++.dg/parse/crash70.C | 14 ++++++++++ 7 files changed, 92 insertions(+), 32 deletions(-) create mode 100644 gcc/testsuite/c-c++-common/Wshadow-1.c create mode 100644 gcc/testsuite/g++.dg/parse/crash70.C diff --git a/gcc/ChangeLog b/gcc/ChangeLog index d1110fced48..d1a83f50d12 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2019-10-30 Bernd Edlinger + + * doc/invoke.texi (-Wshadow, -Wshadow=global + -Wshadow=local, -Wshadow=compatible-local): Update documentation. + 2019-10-30 Tobias Burnus * gimplify.c (gimplify_scan_omp_clauses): Remove FE-generated diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index 6808527d0f5..402d321d0e7 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,10 @@ +2019-10-30 Bernd Edlinger + + PR c++/92024 + * name-lookup.c (check_local_shadow): Shadowing TYPE_DECLs + is always a -Wshadow=compatible-local warning, unless + -Wshadow is used. + 2019-10-30 Jason Merrill * cxx-pretty-print.c (get_fold_operator): Use OVL_OP_INFO. diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c index 9352ce5da0b..9ef1ed9c8e3 100644 --- a/gcc/cp/name-lookup.c +++ b/gcc/cp/name-lookup.c @@ -2750,29 +2750,31 @@ check_local_shadow (tree decl) parameter, more than often they would use the variable thinking (mistakenly) it's still the parameter. It would be rare that users would use the variable in the place that - expects the parameter but thinking it's a new decl. */ + expects the parameter but thinking it's a new decl. + If either object is a TYPE_DECL, '-Wshadow=compatible-local' + warns regardless of whether one of the types involved + is a subclass of the other, since that is never okay. */ enum opt_code warning_code; if (warn_shadow) warning_code = OPT_Wshadow; - else if (warn_shadow_local) - warning_code = OPT_Wshadow_local; - else if (warn_shadow_compatible_local - && (same_type_p (TREE_TYPE (old), TREE_TYPE (decl)) - || (!dependent_type_p (TREE_TYPE (decl)) - && !dependent_type_p (TREE_TYPE (old)) - /* If the new decl uses auto, we don't yet know - its type (the old type cannot be using auto - at this point, without also being - dependent). This is an indication we're - (now) doing the shadow checking too - early. */ - && !type_uses_auto (TREE_TYPE (decl)) - && can_convert (TREE_TYPE (old), TREE_TYPE (decl), - tf_none)))) + else if (same_type_p (TREE_TYPE (old), TREE_TYPE (decl)) + || TREE_CODE (decl) == TYPE_DECL + || TREE_CODE (old) == TYPE_DECL + || (!dependent_type_p (TREE_TYPE (decl)) + && !dependent_type_p (TREE_TYPE (old)) + /* If the new decl uses auto, we don't yet know + its type (the old type cannot be using auto + at this point, without also being + dependent). This is an indication we're + (now) doing the shadow checking too + early. */ + && !type_uses_auto (TREE_TYPE (decl)) + && can_convert (TREE_TYPE (old), TREE_TYPE (decl), + tf_none))) warning_code = OPT_Wshadow_compatible_local; else - return; + warning_code = OPT_Wshadow_local; const char *msg; if (TREE_CODE (old) == PARM_DECL) diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 1407d019d14..d1eb317f43c 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -342,7 +342,7 @@ Objective-C and Objective-C++ Dialects}. -Wno-pragmas -Wno-prio-ctor-dtor -Wredundant-decls @gol -Wrestrict -Wno-return-local-addr @gol -Wreturn-type -Wsequence-point -Wshadow -Wno-shadow-ivar @gol --Wshadow=global, -Wshadow=local, -Wshadow=compatible-local @gol +-Wshadow=global -Wshadow=local -Wshadow=compatible-local @gol -Wshift-overflow -Wshift-overflow=@var{n} @gol -Wshift-count-negative -Wshift-count-overflow -Wshift-negative-value @gol -Wsign-compare -Wsign-conversion -Wfloat-conversion @gol @@ -6309,7 +6309,7 @@ can be used to suppress such a warning. @opindex Wno-discarded-array-qualifiers @opindex Wdiscarded-array-qualifiers Do not warn if type qualifiers on arrays which are pointer targets -are being discarded. Typically, the compiler warns if a +are being discarded. Typically, the compiler warns if a @code{const int (*)[]} variable is passed to a function that takes a @code{int (*)[]} parameter. This option can be used to suppress such a warning. @@ -6508,9 +6508,13 @@ allowed in GCC@. It is not supported by ISO C90. @xref{Mixed Declarations}. @opindex Wno-shadow Warn whenever a local variable or type declaration shadows another variable, parameter, type, class member (in C++), or instance variable -(in Objective-C) or whenever a built-in function is shadowed. Note +(in Objective-C) or whenever a built-in function is shadowed. Note that in C++, the compiler warns if a local variable shadows an explicit typedef, but not if it shadows a struct/class/enum. +If this warning is enabled, it includes also all instances of +local shadowing. This means that @option{-Wno-shadow=local} +and @option{-Wno-shadow=compatible-local} are ignored when +@option{-Wshadow} is used. Same as @option{-Wshadow=global}. @item -Wno-shadow-ivar @r{(Objective-C only)} @@ -6521,20 +6525,19 @@ Objective-C method. @item -Wshadow=global @opindex Wshadow=global -The default for @option{-Wshadow}. Warns for any (global) shadowing. -This warning is enabled by @option{-Wshadow=global}. +Warn for any shadowing. +Same as @option{-Wshadow}. @item -Wshadow=local @opindex Wshadow=local Warn when a local variable shadows another local variable or parameter. -This warning is enabled by @option{-Wshadow=local}. @item -Wshadow=compatible-local @opindex Wshadow=compatible-local Warn when a local variable shadows another local variable or parameter -whose type is compatible with that of the shadowing variable. In C++, +whose type is compatible with that of the shadowing variable. In C++, type compatibility here means the type of the shadowing variable can be -converted to that of the shadowed variable. The creation of this flag +converted to that of the shadowed variable. The creation of this flag (in addition to @option{-Wshadow=local}) is based on the idea that when a local variable shadows another one of incompatible type, it is most likely intentional, not a bug or typo, as shown in the following example: @@ -6553,16 +6556,15 @@ for (SomeIterator i = SomeObj.begin(); i != SomeObj.end(); ++i) @end smallexample Since the two variable @code{i} in the example above have incompatible types, -enabling only @option{-Wshadow=compatible-local} will not emit a warning. +enabling only @option{-Wshadow=compatible-local} does not emit a warning. Because their types are incompatible, if a programmer accidentally uses one -in place of the other, type checking will catch that and emit an error or -warning. So not warning (about shadowing) in this case will not lead to -undetected bugs. Use of this flag instead of @option{-Wshadow=local} can +in place of the other, type checking is expected to catch that and emit an +error or warning. Use of this flag instead of @option{-Wshadow=local} can possibly reduce the number of warnings triggered by intentional shadowing. -Note that this does also mean that shadowing @code{const char *i} by -@code{char *i} will not emit a warning. +Note that this also means that shadowing @code{const char *i} by +@code{char *i} does not emit a warning. -This warning is enabled by @option{-Wshadow=compatible-local}. +This warning is also enabled by @option{-Wshadow=local}. @item -Wlarger-than=@var{byte-size} @opindex Wlarger-than= diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index c2d63003f9b..67de104fb1d 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,9 @@ +2019-10-30 Bernd Edlinger + + PR c++/92024 + * g++.dg/parse/crash70.C: New test. + * c-c++-common/Wshadow-1.c: New test. + 2019-10-30 Tobias Burnus PR fortran/92208 diff --git a/gcc/testsuite/c-c++-common/Wshadow-1.c b/gcc/testsuite/c-c++-common/Wshadow-1.c new file mode 100644 index 00000000000..4d1edf07f00 --- /dev/null +++ b/gcc/testsuite/c-c++-common/Wshadow-1.c @@ -0,0 +1,24 @@ +/* { dg-do-compile } */ +/* { dg-additional-options "-Wshadow=local -Wno-shadow=compatible-local" } */ +int c; +void foo(int *c, int *d) /* { dg-bogus "Wshadow" } */ +{ + int *e = d; + { + int d = 0; /* { dg-warning "Wshadow=local" } */ + } + { + int *e = 0; /* { dg-bogus "Wshadow=compatible-local" } */ + } +} +#pragma GCC diagnostic warning "-Wshadow" +void bar(int *c, int *d) /* { dg-warning "Wshadow" } */ +{ + int *e = d; + { + int d = 0; /* { dg-warning "Wshadow" } */ + } + { + int *e = 0; /* { dg-warning "Wshadow" } */ + } +} diff --git a/gcc/testsuite/g++.dg/parse/crash70.C b/gcc/testsuite/g++.dg/parse/crash70.C new file mode 100644 index 00000000000..16c0785827b --- /dev/null +++ b/gcc/testsuite/g++.dg/parse/crash70.C @@ -0,0 +1,14 @@ +// PR c++/92024 +// { dg-additional-options "-Wshadow=compatible-local" } + +template +struct S { + S () { + struct c; + { + struct c {}; // { dg-warning "Wshadow=compatible-local" } + } + } +}; + +S s; -- 2.30.2