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.
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 | 18 +++++++------ gcc/testsuite/c-c++-common/Winit-self1.c | 32 ++++++++++++++++++++++++ gcc/testsuite/c-c++-common/Winit-self2.c | 31 +++++++++++++++++++++++ 3 files changed, 74 insertions(+), 7 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..2e011830846 100644 --- a/gcc/c-family/c-gimplify.cc +++ b/gcc/c-family/c-gimplify.cc @@ -712,13 +712,17 @@ c_gimplify_expr (tree *expr_p, gimple_seq *pre_p ATTRIBUTE_UNUSED, /* 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; + { + tree &decl = DECL_EXPR_DECL (*expr_p); + if (VAR_P (decl) + && !DECL_EXTERNAL (decl) + && !TREE_STATIC (decl) + && (DECL_INITIAL (decl) + && tree_strip_nop_conversions (DECL_INITIAL (decl)) == decl) + && !warn_init_self) + suppress_warning (decl, OPT_Winit_self); + break; + }case PREINCREMENT_EXPR:case PREDECREMENT_EXPR: 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..2a1a755fc71 --- /dev/null +++ b/gcc/testsuite/c-c++-common/Winit-self1.c @@ -0,0 +1,32 @@ +/* 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 () +{ + /* ??? Do we want this warning in C++? Probably not with -Wno-init-self. */ + volatile int k = k; /* { dg-warning "used uninitialized" "" { target c++ } } */ + return k; +} + +int +fn4 () +{ + const volatile int l = l; /* { dg-warning "used uninitialized" "" { target c++ } } */ + 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: 600956c81c784f4a0cc9d10f6e03e01847afd961
