On Sat, Aug 06, 2022 at 03:29:05PM -0700, Jason Merrill wrote: > On 7/26/22 14:31, Marek Polacek wrote: > > On Tue, Jul 26, 2022 at 04:24:18PM -0400, Jason Merrill wrote: > > > On 7/26/22 15:03, Marek Polacek wrote: > > > > Since r11-5188-g32934a4f45a721, we drop qualifiers during l-to-r > > > > conversion by creating a NOP_EXPR. For e.g. > > > > > > > > const int i = i; > > > > > > > > that means that the DECL_INITIAL is '(int) i' and not 'i' anymore. > > > > Consequently, we don't suppress_warning here: > > > > > > > > 711 case DECL_EXPR: > > > > 715 if (VAR_P (DECL_EXPR_DECL (*expr_p)) > > > > 716 && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p)) > > > > 717 && !TREE_STATIC (DECL_EXPR_DECL (*expr_p)) > > > > 718 && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p)) == > > > > DECL_EXPR_DECL (*expr_p)) > > > > 719 && !warn_init_self) > > > > 720 suppress_warning (DECL_EXPR_DECL (*expr_p), OPT_Winit_self); > > > > > > > > because of the check on line 718 -- (int) i is not i. So -Wno-init-self > > > > doesn't disable the warning as it's supposed to. > > > > > > > > The following patch fixes it...except it doesn't, for volatile variables > > > > in C++. The problem is that for > > > > > > > > volatile int k = k; > > > > > > > > we see that the initializer has TREE_SIDE_EFFECTS, so we perform dynamic > > > > initialization. So there's no DECL_INITIAL and the suppress_warning > > > > call above is never done. I suppose we could amend > > > > get_no_uninit_warning > > > > to return true for volatile-qualified expressions. I mean, can we ever > > > > say for a fact that a volatile variable is uninitialized? > > > > > > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > > > > > > > PR middle-end/102633 > > > > > > > > gcc/c-family/ChangeLog: > > > > > > > > * c-gimplify.cc (c_gimplify_expr): Strip NOPs of DECL_INITIAL. > > > > > > I wonder if we want to handle this i = i case earlier, like in > > > finish_decl. > > > > I could, something like > > > > @@ -5381,7 +5381,14 @@ finish_decl (tree decl, location_t init_loc, tree > > init, > > init = NULL_TREE; > > > > if (init) > > - store_init_value (init_loc, decl, init, origtype); > > + { > > + /* In the self-init case, undo the artificial NOP_EXPR we may have > > + added in convert_lvalue_to_rvalue so that c_gimplify_expr/DECL_EXPR > > + can perform suppress_warning. */ > > + if (TREE_CODE (init) == NOP_EXPR && TREE_OPERAND (init, 0) == decl) > > + init = TREE_OPERAND (init, 0); > > + store_init_value (init_loc, decl, init, origtype); > > + } > > > > but then I'd have to do the same thing in cp_finish_decl because > > decay_conversion also adds a NOP_EXPR for cv-qualified non-class prvalues. > > Is that what we want? To me that seems less clean than having > > c_gimplify_expr > > see through NOP_EXPRs. > > I was thinking of checking the form of the initializer before > decay_conversion or anything else messes with it, and calling > suppress_warning at that point instead of in c_gimplify_expr.
Aaah, okay. Here's a patch that does it. In the C FE it has to happen really early. Now both front ends behave the same wrt volatiles! Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? -- >8 -- Since r11-5188-g32934a4f45a721, we drop qualifiers during l-to-r conversion by creating a NOP_EXPR. For e.g. const int i = i; that means that the DECL_INITIAL is '(int) i' and not 'i' anymore. Consequently, we don't suppress_warning here: 711 case DECL_EXPR: 715 if (VAR_P (DECL_EXPR_DECL (*expr_p)) 716 && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p)) 717 && !TREE_STATIC (DECL_EXPR_DECL (*expr_p)) 718 && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p)) == DECL_EXPR_DECL (*expr_p)) 719 && !warn_init_self) 720 suppress_warning (DECL_EXPR_DECL (*expr_p), OPT_Winit_self); because of the check on line 718 -- (int) i is not i. So -Wno-init-self doesn't disable the warning as it's supposed to. The following patch fixes it by moving the suppress_warning call from c_gimplify_expr to the front ends, at points where we haven't created the NOP_EXPR yet. PR middle-end/102633 gcc/c-family/ChangeLog: * c-gimplify.cc (c_gimplify_expr) <case DECL_EXPR>: Don't call suppress_warning here. gcc/c/ChangeLog: * c-parser.cc (c_parser_initializer): Add new tree parameter. Use it. Call suppress_warning. (c_parser_declaration_or_fndef): Pass d down to c_parser_initializer. (c_parser_omp_declare_reduction): Pass omp_priv down to c_parser_initializer. gcc/cp/ChangeLog: * decl.cc (cp_finish_decl): Call suppress_warning. gcc/testsuite/ChangeLog: * c-c++-common/Winit-self1.c: New test. * c-c++-common/Winit-self2.c: New test. --- gcc/c-family/c-gimplify.cc | 12 --------- gcc/c/c-parser.cc | 19 ++++++++++++--- gcc/cp/decl.cc | 8 ++++++ gcc/testsuite/c-c++-common/Winit-self1.c | 31 ++++++++++++++++++++++++ gcc/testsuite/c-c++-common/Winit-self2.c | 31 ++++++++++++++++++++++++ 5 files changed, 85 insertions(+), 16 deletions(-) create mode 100644 gcc/testsuite/c-c++-common/Winit-self1.c create mode 100644 gcc/testsuite/c-c++-common/Winit-self2.c diff --git a/gcc/c-family/c-gimplify.cc b/gcc/c-family/c-gimplify.cc index a6f26c9b0d3..039a4b93230 100644 --- a/gcc/c-family/c-gimplify.cc +++ b/gcc/c-family/c-gimplify.cc @@ -708,18 +708,6 @@ c_gimplify_expr (tree *expr_p, gimple_seq *pre_p ATTRIBUTE_UNUSED, break; } - case DECL_EXPR: - /* This is handled mostly by gimplify.cc, but we have to deal with - not warning about int x = x; as it is a GCC extension to turn off - this warning but only if warn_init_self is zero. */ - if (VAR_P (DECL_EXPR_DECL (*expr_p)) - && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p)) - && !TREE_STATIC (DECL_EXPR_DECL (*expr_p)) - && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p)) == DECL_EXPR_DECL (*expr_p)) - && !warn_init_self) - suppress_warning (DECL_EXPR_DECL (*expr_p), OPT_Winit_self); - break; - case PREINCREMENT_EXPR: case PREDECREMENT_EXPR: case POSTINCREMENT_EXPR: diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc index 92049d1a101..6ed17ed9c48 100644 --- a/gcc/c/c-parser.cc +++ b/gcc/c/c-parser.cc @@ -1521,7 +1521,7 @@ static struct c_arg_info *c_parser_parms_list_declarator (c_parser *, tree, static struct c_parm *c_parser_parameter_declaration (c_parser *, tree, bool); static tree c_parser_simple_asm_expr (c_parser *); static tree c_parser_gnu_attributes (c_parser *); -static struct c_expr c_parser_initializer (c_parser *); +static struct c_expr c_parser_initializer (c_parser *, tree); static struct c_expr c_parser_braced_init (c_parser *, tree, bool, struct obstack *); static void c_parser_initelt (c_parser *, struct obstack *); @@ -2286,7 +2286,7 @@ c_parser_declaration_or_fndef (c_parser *parser, bool fndef_ok, int flag_sanitize_save = flag_sanitize; if (TREE_CODE (d) == PARM_DECL) flag_sanitize = 0; - init = c_parser_initializer (parser); + init = c_parser_initializer (parser, d); flag_sanitize = flag_sanitize_save; finish_init (); } @@ -5211,11 +5211,13 @@ c_parser_type_name (c_parser *parser, bool alignas_ok) Any expression without commas is accepted in the syntax for the constant-expressions, with non-constant expressions rejected later. + DECL is the declaration we're parsing this initializer for. + This function is only used for top-level initializers; for nested ones, see c_parser_initval. */ static struct c_expr -c_parser_initializer (c_parser *parser) +c_parser_initializer (c_parser *parser, tree decl) { if (c_parser_next_token_is (parser, CPP_OPEN_BRACE)) return c_parser_braced_init (parser, NULL_TREE, false, NULL); @@ -5224,6 +5226,15 @@ c_parser_initializer (c_parser *parser) struct c_expr ret; location_t loc = c_parser_peek_token (parser)->location; ret = c_parser_expr_no_commas (parser, NULL); + /* This is handled mostly by gimplify.cc, but we have to deal with + not warning about int x = x; as it is a GCC extension to turn off + this warning but only if warn_init_self is zero. */ + if (VAR_P (decl) + && !DECL_EXTERNAL (decl) + && !TREE_STATIC (decl) + && ret.value == decl + && !warn_init_self) + suppress_warning (decl, OPT_Winit_self); if (TREE_CODE (ret.value) != STRING_CST && TREE_CODE (ret.value) != COMPOUND_LITERAL_EXPR) ret = convert_lvalue_to_rvalue (loc, ret, true, true); @@ -22576,7 +22587,7 @@ c_parser_omp_declare_reduction (c_parser *parser, enum pragma_context context) location_t loc = c_parser_peek_token (parser)->location; rich_location richloc (line_table, loc); start_init (omp_priv, NULL_TREE, 0, &richloc); - struct c_expr init = c_parser_initializer (parser); + struct c_expr init = c_parser_initializer (parser, omp_priv); finish_init (); finish_decl (omp_priv, loc, init.value, init.original_type, NULL_TREE); diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc index 70ad681467e..ff56fddba54 100644 --- a/gcc/cp/decl.cc +++ b/gcc/cp/decl.cc @@ -8253,6 +8253,14 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p, && !TYPE_REF_P (type)) TREE_CONSTANT (decl) = 1; } + /* This is handled mostly by gimplify.cc, but we have to deal with + not warning about int x = x; as it is a GCC extension to turn off + this warning but only if warn_init_self is zero. */ + if (!DECL_EXTERNAL (decl) + && !TREE_STATIC (decl) + && decl == tree_strip_any_location_wrapper (init) + && !warn_init_self) + suppress_warning (decl, OPT_Winit_self); } if (flag_openmp diff --git a/gcc/testsuite/c-c++-common/Winit-self1.c b/gcc/testsuite/c-c++-common/Winit-self1.c new file mode 100644 index 00000000000..740b83b5e9f --- /dev/null +++ b/gcc/testsuite/c-c++-common/Winit-self1.c @@ -0,0 +1,31 @@ +/* PR middle-end/102633 */ +/* { dg-do compile } */ +/* { dg-options "-Wuninitialized -Wno-init-self" } */ + +int +fn1 (void) +{ + int i = i; + return i; +} + +int +fn2 () +{ + const int j = j; + return j; +} + +int +fn3 () +{ + volatile int k = k; + return k; +} + +int +fn4 () +{ + const volatile int l = l; + return l; +} diff --git a/gcc/testsuite/c-c++-common/Winit-self2.c b/gcc/testsuite/c-c++-common/Winit-self2.c new file mode 100644 index 00000000000..13aa9efdf26 --- /dev/null +++ b/gcc/testsuite/c-c++-common/Winit-self2.c @@ -0,0 +1,31 @@ +/* PR middle-end/102633 */ +/* { dg-do compile } */ +/* { dg-options "-Wuninitialized -Winit-self" } */ + +int +fn1 (void) +{ + int i = i; /* { dg-warning "used uninitialized" } */ + return i; +} + +int +fn2 () +{ + const int j = j; /* { dg-warning "used uninitialized" } */ + return j; +} + +int +fn3 () +{ + volatile int k = k; /* { dg-warning "used uninitialized" } */ + return k; +} + +int +fn4 () +{ + const volatile int l = l; /* { dg-warning "used uninitialized" } */ + return l; +} base-commit: 21c7aab09805d0c8c7695c8a69c8715d673a739a -- 2.37.1