On Wed, Nov 22, 2023 at 11:45 PM Jason Merrill <ja...@redhat.com> wrote:
>
> Tested x86_64-pc-linux-gnu, OK for trunk?
OK
> -- 8< --
>
> -Waddress-of-packed-member, in addition to the documented warning about
> taking the address of a packed member, also warns about casting from
> a pointer to a TYPE_PACKED type to a pointer to a type with greater
> alignment.
>
> This wrongly warns if the source is a pointer to enum when -fshort-enums
> is on, since that is also represented by TYPE_PACKED.
>
> And there's already -Wcast-align to catch casting from pointer to less
> aligned type (packed or otherwise) to pointer to more aligned type; even
> apart from the enum problem, this seems like a somewhat arbitrary subset of
> that warning. Though that isn't currently on by default.
>
> So, this patch removes the undocumented type-based warning from
> -Waddress-of-packed-member. Some of the tests where the warning is
> desirable I changed to use -Wcast-align=strict instead. The ones that
> require -Wno-incompatible-pointer-types, I just removed.
>
> gcc/c-family/ChangeLog:
>
> * c-warn.cc (check_address_or_pointer_of_packed_member):
> Remove warning based on TYPE_PACKED.
>
> gcc/testsuite/ChangeLog:
>
> * c-c++-common/Waddress-of-packed-member-1.c: Don't expect
> a warning on the cast cases.
> * c-c++-common/pr51628-35.c: Use -Wcast-align=strict.
> * g++.dg/warn/Waddress-of-packed-member3.C: Likewise.
> * gcc.dg/pr88928.c: Likewise.
> * gcc.dg/pr51628-20.c: Removed.
> * gcc.dg/pr51628-21.c: Removed.
> * gcc.dg/pr51628-25.c: Removed.
> ---
> gcc/c-family/c-warn.cc | 58 +------------------
> .../Waddress-of-packed-member-1.c | 12 ++--
> gcc/testsuite/c-c++-common/pr51628-35.c | 6 +-
> .../g++.dg/warn/Waddress-of-packed-member3.C | 8 +--
> gcc/testsuite/gcc.dg/pr51628-20.c | 11 ----
> gcc/testsuite/gcc.dg/pr51628-21.c | 11 ----
> gcc/testsuite/gcc.dg/pr51628-25.c | 9 ---
> gcc/testsuite/gcc.dg/pr88928.c | 6 +-
> 8 files changed, 19 insertions(+), 102 deletions(-)
> delete mode 100644 gcc/testsuite/gcc.dg/pr51628-20.c
> delete mode 100644 gcc/testsuite/gcc.dg/pr51628-21.c
> delete mode 100644 gcc/testsuite/gcc.dg/pr51628-25.c
>
> diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc
> index d2938b91043..2a399ba6d14 100644
> --- a/gcc/c-family/c-warn.cc
> +++ b/gcc/c-family/c-warn.cc
> @@ -2991,10 +2991,9 @@ check_alignment_of_packed_member (tree type, tree
> field, bool rvalue)
> return NULL_TREE;
> }
>
> -/* Return struct or union type if the right hand value, RHS:
> - 1. Is a pointer value which isn't aligned to a pointer type TYPE.
> - 2. Is an address which takes the unaligned address of packed member
> - of struct or union when assigning to TYPE.
> +/* Return struct or union type if the right hand value, RHS
> + is an address which takes the unaligned address of packed member
> + of struct or union when assigning to TYPE.
> Otherwise, return NULL_TREE. */
>
> static tree
> @@ -3021,57 +3020,6 @@ check_address_or_pointer_of_packed_member (tree type,
> tree rhs)
>
> type = TREE_TYPE (type);
>
> - if (TREE_CODE (rhs) == PARM_DECL
> - || VAR_P (rhs)
> - || TREE_CODE (rhs) == CALL_EXPR)
> - {
> - tree rhstype = TREE_TYPE (rhs);
> - if (TREE_CODE (rhs) == CALL_EXPR)
> - {
> - rhs = CALL_EXPR_FN (rhs); /* Pointer expression. */
> - if (rhs == NULL_TREE)
> - return NULL_TREE;
> - rhs = TREE_TYPE (rhs); /* Pointer type. */
> - /* We could be called while processing a template and RHS could be
> - a functor. In that case it's a class, not a pointer. */
> - if (!rhs || !POINTER_TYPE_P (rhs))
> - return NULL_TREE;
> - rhs = TREE_TYPE (rhs); /* Function type. */
> - rhstype = TREE_TYPE (rhs);
> - if (!rhstype || !POINTER_TYPE_P (rhstype))
> - return NULL_TREE;
> - rvalue = true;
> - }
> - if (rvalue && POINTER_TYPE_P (rhstype))
> - rhstype = TREE_TYPE (rhstype);
> - while (TREE_CODE (rhstype) == ARRAY_TYPE)
> - rhstype = TREE_TYPE (rhstype);
> - if (TYPE_PACKED (rhstype))
> - {
> - unsigned int type_align = min_align_of_type (type);
> - unsigned int rhs_align = min_align_of_type (rhstype);
> - if (rhs_align < type_align)
> - {
> - auto_diagnostic_group d;
> - location_t location = EXPR_LOC_OR_LOC (rhs, input_location);
> - if (warning_at (location, OPT_Waddress_of_packed_member,
> - "converting a packed %qT pointer (alignment %d)
> "
> - "to a %qT pointer (alignment %d) may result in "
> - "an unaligned pointer value",
> - rhstype, rhs_align, type, type_align))
> - {
> - tree decl = TYPE_STUB_DECL (rhstype);
> - if (decl)
> - inform (DECL_SOURCE_LOCATION (decl), "defined here");
> - decl = TYPE_STUB_DECL (type);
> - if (decl)
> - inform (DECL_SOURCE_LOCATION (decl), "defined here");
> - }
> - }
> - }
> - return NULL_TREE;
> - }
> -
> tree context = NULL_TREE;
>
> /* Check alignment of the object. */
> diff --git a/gcc/testsuite/c-c++-common/Waddress-of-packed-member-1.c
> b/gcc/testsuite/c-c++-common/Waddress-of-packed-member-1.c
> index 95a376664da..0f5188df70a 100644
> --- a/gcc/testsuite/c-c++-common/Waddress-of-packed-member-1.c
> +++ b/gcc/testsuite/c-c++-common/Waddress-of-packed-member-1.c
> @@ -52,12 +52,12 @@ void foo (void)
> f0 = *&__real__ t0.f; /* { dg-bogus "may result in an unaligned
> pointer value" } */
> f0 = *&__imag__ t0.f; /* { dg-bogus "may result in an unaligned
> pointer value" } */
> i1 = (&t0.c, (int*) 0); /* { dg-bogus "may result in an unaligned
> pointer value" } */
> - t2 = (struct t**) t10; /* { dg-warning "may result in an unaligned
> pointer value" "" { target { ! default_packed } } } */
> - t2 = (struct t**) t100; /* { dg-warning "may result in an unaligned
> pointer value" "" { target { ! default_packed } } } */
> - t2 = (struct t**) t1; /* { dg-warning "may result in an unaligned
> pointer value" "" { target { ! default_packed } } } */
> - t2 = (struct t**) bar(); /* { dg-warning "may result in an unaligned
> pointer value" "" { target { ! default_packed } } } */
> - t2 = (struct t**) baz(); /* { dg-warning "may result in an unaligned
> pointer value" "" { target { ! default_packed } } } */
> - t2 = (struct t**) bazz(); /* { dg-warning "may result in an unaligned
> pointer value" "" { target { ! default_packed } } } */
> + t2 = (struct t**) t10; /* { dg-bogus "may result in an unaligned
> pointer value" } */
> + t2 = (struct t**) t100; /* { dg-bogus "may result in an unaligned
> pointer value" } */
> + t2 = (struct t**) t1; /* { dg-bogus "may result in an unaligned
> pointer value" } */
> + t2 = (struct t**) bar(); /* { dg-bogus "may result in an unaligned
> pointer value" } */
> + t2 = (struct t**) baz(); /* { dg-bogus "may result in an unaligned
> pointer value" } */
> + t2 = (struct t**) bazz(); /* { dg-bogus "may result in an unaligned
> pointer value" } */
> i1 = &t0.b; /* { dg-warning "may result in an unaligned
> pointer value" "" { target { ! default_packed } } } */
> i1 = &t1->b; /* { dg-warning "may result in an unaligned
> pointer value" "" { target { ! default_packed } } } */
> i1 = &t10[0].b; /* { dg-warning "may result in an unaligned
> pointer value" "" { target { ! default_packed } } } */
> diff --git a/gcc/testsuite/c-c++-common/pr51628-35.c
> b/gcc/testsuite/c-c++-common/pr51628-35.c
> index fa37d99beb7..a88c19ea0df 100644
> --- a/gcc/testsuite/c-c++-common/pr51628-35.c
> +++ b/gcc/testsuite/c-c++-common/pr51628-35.c
> @@ -1,6 +1,6 @@
> /* PR c/51628. */
> /* { dg-do compile } */
> -/* { dg-options "-O" } */
> +/* { dg-options "-O -Wcast-align=strict" } */
>
> struct B { int i; };
> struct C { struct B b; } __attribute__ ((packed));
> @@ -12,12 +12,12 @@ long *
> foo1 (void)
> {
> return (long *) p;
> -/* { dg-warning "may result in an unaligned pointer value" "" { target { !
> default_packed } } .-1 } */
> +/* { dg-warning "increases required alignment" "" { target { !
> default_packed } } .-1 } */
> }
>
> long *
> foo2 (void)
> {
> return (long *) bar ();
> -/* { dg-warning "may result in an unaligned pointer value" "" { target { !
> default_packed } } .-1 } */
> +/* { dg-warning "increases required alignment" "" { target { !
> default_packed } } .-1 } */
> }
> diff --git a/gcc/testsuite/g++.dg/warn/Waddress-of-packed-member3.C
> b/gcc/testsuite/g++.dg/warn/Waddress-of-packed-member3.C
> index aeffb969c01..28dd05d366c 100644
> --- a/gcc/testsuite/g++.dg/warn/Waddress-of-packed-member3.C
> +++ b/gcc/testsuite/g++.dg/warn/Waddress-of-packed-member3.C
> @@ -1,5 +1,5 @@
> // { dg-do compile { target { ! default_packed } } }
> -// Test that -Waddress-of-packed-member works with member functions.
> +// { dg-additional-options -Wcast-align=strict }
>
> struct S {
> char c;
> @@ -16,8 +16,8 @@ S**
> f ()
> {
> S **s;
> - s = reinterpret_cast<S**>(foo ()); // { dg-warning "converting a packed" }
> - s = reinterpret_cast<S**>(x.memfn ()); // { dg-warning "converting a
> packed" }
> - s = reinterpret_cast<S**>(X::smemfn ()); // { dg-warning "converting a
> packed" }
> + s = reinterpret_cast<S**>(foo ()); // { dg-warning "increases required
> alignment" }
> + s = reinterpret_cast<S**>(x.memfn ()); // { dg-warning "increases required
> alignment" }
> + s = reinterpret_cast<S**>(X::smemfn ()); // { dg-warning "increases
> required alignment" }
> return s;
> }
> diff --git a/gcc/testsuite/gcc.dg/pr51628-20.c
> b/gcc/testsuite/gcc.dg/pr51628-20.c
> deleted file mode 100644
> index 2249d85098b..00000000000
> --- a/gcc/testsuite/gcc.dg/pr51628-20.c
> +++ /dev/null
> @@ -1,11 +0,0 @@
> -/* PR c/51628. */
> -/* { dg-do compile } */
> -/* { dg-options "-O -Wno-incompatible-pointer-types" } */
> -
> -struct B { int i; };
> -struct C { struct B b; } __attribute__ ((packed));
> -
> -extern struct C *p;
> -
> -long* g8 (void) { return p; }
> -/* { dg-warning "may result in an unaligned pointer value" "" { target { !
> default_packed } } .-1 } */
> diff --git a/gcc/testsuite/gcc.dg/pr51628-21.c
> b/gcc/testsuite/gcc.dg/pr51628-21.c
> deleted file mode 100644
> index f1adbe64002..00000000000
> --- a/gcc/testsuite/gcc.dg/pr51628-21.c
> +++ /dev/null
> @@ -1,11 +0,0 @@
> -/* PR c/51628. */
> -/* { dg-do compile } */
> -/* { dg-options "-O -Wno-incompatible-pointer-types" } */
> -
> -struct B { int i; };
> -struct C { struct B b; } __attribute__ ((packed));
> -
> -extern struct C p[];
> -
> -long* g8 (void) { return p; }
> -/* { dg-warning "may result in an unaligned pointer value" "" { target { !
> default_packed } } .-1 } */
> diff --git a/gcc/testsuite/gcc.dg/pr51628-25.c
> b/gcc/testsuite/gcc.dg/pr51628-25.c
> deleted file mode 100644
> index f00d9b1bcac..00000000000
> --- a/gcc/testsuite/gcc.dg/pr51628-25.c
> +++ /dev/null
> @@ -1,9 +0,0 @@
> -/* PR c/51628. */
> -/* { dg-do compile } */
> -/* { dg-options "-O -Wno-incompatible-pointer-types" } */
> -
> -struct B { int i; };
> -struct C { struct B b; } __attribute__ ((packed));
> -
> -long* g8 (struct C *p) { return p; }
> -/* { dg-warning "may result in an unaligned pointer value" "" { target { !
> default_packed } } .-1 } */
> diff --git a/gcc/testsuite/gcc.dg/pr88928.c b/gcc/testsuite/gcc.dg/pr88928.c
> index 0b6c1d70f05..1d176d6d51d 100644
> --- a/gcc/testsuite/gcc.dg/pr88928.c
> +++ b/gcc/testsuite/gcc.dg/pr88928.c
> @@ -1,6 +1,6 @@
> -/* { dg-do compile } */
> -/* { dg-options "-Wno-pedantic -Waddress-of-packed-member" } */
> +/* { dg-do compile { target { ! default_packed } } } */
> +/* { dg-options "-Wno-pedantic -Waddress-of-packed-member
> -Wcast-align=strict" } */
> struct a { } __attribute__((__packed__));
> void c (struct a **);
> void d (const struct a *b) { c ((struct a **) b); }
> -/* { dg-warning "may result in an unaligned pointer value" "" { target { !
> default_packed } } .-1 } */
> +/* { dg-warning "increases required alignment" "" { target *-*-* } .-1 } */
>
> base-commit: 65bd6de0de57abc86931a5e0b9a8d453ad530004
> --
> 2.39.3
>
