[PING] Re: [PATCH 1/2] c-family: -Waddress-of-packed-member and casts

[Torbjorn SVENSSON <torbjorn.svensson@foss.st.com>]

Ping!

Kind regards,
Torbjörn


On 2024-02-07 17:19, Torbjorn SVENSSON wrote:
> Hi,
> 
> Is it okay to backport b7e4a4c626eeeb32c291d5bbbaa148c5081b6bfd to 
> releases/gcc-13?
> 
> Without this backport, I see these failures on arm-none-eabi:
> 
> FAIL: 
> gcc.dg/analyzer/null-deref-pr108251-smp_fetch_ssl_fc_has_early-O2.c 
> (test for excess errors)
> FAIL: gcc.dg/analyzer/null-deref-pr108251-smp_fetch_ssl_fc_has_early.c 
> (test for excess errors)
> 
> Kind regards,
> Torbjörn
> 
> On 2023-12-11 08:28, Richard Biener wrote:
>> On Wed, Nov 22, 2023 at 11:45 PM Jason Merrill <jason@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
>>>