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From: Marek Polacek <mpolacek@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-6060] warn-access: wrong -Wdangling-pointer with labels [PR106080] Date: Wed, 15 Feb 2023 13:57:01 +0000 (GMT) [thread overview] Message-ID: <20230215135701.2D18C3858C60@sourceware.org> (raw) https://gcc.gnu.org/g:d482b20fd346482635a770281a164a09d608b058 commit r13-6060-gd482b20fd346482635a770281a164a09d608b058 Author: Marek Polacek <polacek@redhat.com> Date: Tue Feb 14 17:05:44 2023 -0500 warn-access: wrong -Wdangling-pointer with labels [PR106080] -Wdangling-pointer warns when the address of a label escapes. This causes grief in OCaml (<https://github.com/ocaml/ocaml/issues/11358>) as well as in the kernel: <https://bugzilla.kernel.org/show_bug.cgi?id=215851> because it uses #define _THIS_IP_ ({ __label__ __here; __here: (unsigned long)&&__here; }) to get the PC. -Wdangling-pointer is documented to warn about pointers to objects. However, it uses is_auto_decl which checks DECL_P, but DECL_P is also true for a label/enumerator/function declaration, none of which is an object. Rather, it should use auto_var_p which correctly checks VAR_P and PARM_DECL. PR middle-end/106080 gcc/ChangeLog: * gimple-ssa-warn-access.cc (is_auto_decl): Remove. Use auto_var_p instead. gcc/testsuite/ChangeLog: * c-c++-common/Wdangling-pointer-10.c: New test. * c-c++-common/Wdangling-pointer-9.c: New test. Diff: --- gcc/gimple-ssa-warn-access.cc | 19 +++++-------------- gcc/testsuite/c-c++-common/Wdangling-pointer-10.c | 12 ++++++++++++ gcc/testsuite/c-c++-common/Wdangling-pointer-9.c | 9 +++++++++ 3 files changed, 26 insertions(+), 14 deletions(-) diff --git a/gcc/gimple-ssa-warn-access.cc b/gcc/gimple-ssa-warn-access.cc index ad9dac54874..2eab1d59abd 100644 --- a/gcc/gimple-ssa-warn-access.cc +++ b/gcc/gimple-ssa-warn-access.cc @@ -4326,15 +4326,6 @@ pass_waccess::check_call (gcall *stmt) check_nonstring_args (stmt); } - -/* Return true of X is a DECL with automatic storage duration. */ - -static inline bool -is_auto_decl (tree x) -{ - return DECL_P (x) && !DECL_EXTERNAL (x) && !TREE_STATIC (x); -} - /* Check non-call STMT for invalid accesses. */ void @@ -4363,7 +4354,7 @@ pass_waccess::check_stmt (gimple *stmt) while (handled_component_p (lhs)) lhs = TREE_OPERAND (lhs, 0); - if (is_auto_decl (lhs)) + if (auto_var_p (lhs)) m_clobbers.remove (lhs); return; } @@ -4383,7 +4374,7 @@ pass_waccess::check_stmt (gimple *stmt) while (handled_component_p (arg)) arg = TREE_OPERAND (arg, 0); - if (!is_auto_decl (arg)) + if (!auto_var_p (arg)) return; gimple **pclobber = m_clobbers.get (arg); @@ -4467,7 +4458,7 @@ void pass_waccess::check_dangling_uses (tree var, tree decl, bool maybe /* = false */, bool objref /* = false */) { - if (!decl || !is_auto_decl (decl)) + if (!decl || !auto_var_p (decl)) return; gimple **pclob = m_clobbers.get (decl); @@ -4528,7 +4519,7 @@ pass_waccess::check_dangling_stores (basic_block bb, if (!m_ptr_qry.get_ref (lhs, stmt, &lhs_ref, 0)) continue; - if (is_auto_decl (lhs_ref.ref)) + if (auto_var_p (lhs_ref.ref)) continue; if (DECL_P (lhs_ref.ref)) @@ -4573,7 +4564,7 @@ pass_waccess::check_dangling_stores (basic_block bb, || rhs_ref.deref != -1) continue; - if (!is_auto_decl (rhs_ref.ref)) + if (!auto_var_p (rhs_ref.ref)) continue; auto_diagnostic_group d; diff --git a/gcc/testsuite/c-c++-common/Wdangling-pointer-10.c b/gcc/testsuite/c-c++-common/Wdangling-pointer-10.c new file mode 100644 index 00000000000..ef553bdf2ce --- /dev/null +++ b/gcc/testsuite/c-c++-common/Wdangling-pointer-10.c @@ -0,0 +1,12 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -Wdangling-pointer" } */ + +struct S { + int x; +}; + +void g (int **p) +{ + struct S s = {}; + *p = &s.x; /* { dg-warning "address of local variable" } */ +} diff --git a/gcc/testsuite/c-c++-common/Wdangling-pointer-9.c b/gcc/testsuite/c-c++-common/Wdangling-pointer-9.c new file mode 100644 index 00000000000..f6c92855404 --- /dev/null +++ b/gcc/testsuite/c-c++-common/Wdangling-pointer-9.c @@ -0,0 +1,9 @@ +/* PR middle-end/106080 */ +/* { dg-do compile } */ +/* { dg-options "-O2 -Wdangling-pointer" } */ + +void +foo (void **failaddr) +{ + *failaddr = ({ __label__ __here; __here: &&__here; }); /* { dg-bogus "address of local variable" } */ +}
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