* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
[not found] <bug-88115-4@http.gcc.gnu.org/bugzilla/>
@ 2020-10-05 9:22 ` redi at gcc dot gnu.org
2020-10-07 14:52 ` cvs-commit at gcc dot gnu.org
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To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88115
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=97273
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
Last reconfirmed| |2020-10-05
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
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To: gcc-bugs
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--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:
https://gcc.gnu.org/g:592fe221735bdaa375b1834dd49ce125d0b600d8
commit r11-3704-g592fe221735bdaa375b1834dd49ce125d0b600d8
Author: Patrick Palka <ppalka@redhat.com>
Date: Wed Oct 7 10:49:00 2020 -0400
c++: Distinguish alignof and __alignof__ in cp_tree_equal [PR97273]
cp_tree_equal currently considers alignof the same as __alignof__, but
these operators are semantically different ever since r8-7957. In the
testcase below, this causes the second static_assert to fail on targets
where alignof(double) != __alignof__(double) because the specialization
table (which uses cp_tree_equal as its equality predicate) conflates the
two dependent specializations integral_constant<__alignof__(T)> and
integral_constant<alignof(T)>.
This patch makes cp_tree_equal distinguish between these two operators
by inspecting the ALIGNOF_EXPR_STD_P flag.
gcc/cp/ChangeLog:
PR c++/88115
PR libstdc++/97273
* tree.c (cp_tree_equal) <case ALIGNOF_EXPR>: Return false if
ALIGNOF_EXPR_STD_P differ.
gcc/testsuite/ChangeLog:
PR c++/88115
PR libstdc++/97273
* g++.dg/template/alignof3.C: New test.
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
[not found] <bug-88115-4@http.gcc.gnu.org/bugzilla/>
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To: gcc-bugs
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--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:
https://gcc.gnu.org/g:aeb69dda51e93379fce10fb03ec57650fbf73f31
commit r10-8872-gaeb69dda51e93379fce10fb03ec57650fbf73f31
Author: Patrick Palka <ppalka@redhat.com>
Date: Thu Oct 8 19:31:57 2020 -0400
c++: Distinguish alignof and __alignof__ in cp_tree_equal [PR97273]
cp_tree_equal currently considers alignof the same as __alignof__, but
these operators are semantically different ever since r8-7957. In the
testcase below, this causes the second static_assert to fail on targets
where alignof(double) != __alignof__(double) because the specialization
table (which uses cp_tree_equal as its equality predicate) conflates the
two dependent specializations integral_constant<__alignof__(T)> and
integral_constant<alignof(T)>.
This patch makes cp_tree_equal distinguish between these two operators
by inspecting the ALIGNOF_EXPR_STD_P flag.
gcc/cp/ChangeLog:
PR c++/88115
PR libstdc++/97273
* tree.c (cp_tree_equal) <case ALIGNOF_EXPR>: Return false if
ALIGNOF_EXPR_STD_P differ.
gcc/testsuite/ChangeLog:
PR c++/88115
PR libstdc++/97273
* g++.dg/template/alignof3.C: New test.
(cherry picked from commit 592fe221735bdaa375b1834dd49ce125d0b600d8)
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
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To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88115
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:
https://gcc.gnu.org/g:61827d5d9a5a09a8c05d5e41f95b03ebc6c43f61
commit r11-4925-g61827d5d9a5a09a8c05d5e41f95b03ebc6c43f61
Author: Patrick Palka <ppalka@redhat.com>
Date: Wed Nov 11 14:43:39 2020 -0500
c++: Correct the handling of alignof(expr) [PR88115]
We're currently neglecting to set the ALIGNOF_EXPR_STD_P flag on an
ALIGNOF_EXPR when its operand is an expression. This leads to us
handling alignof(expr) as if it were written __alignof__(expr), and
returning the preferred alignment instead of the ABI alignment. In the
testcase below, this causes the first and third static_assert to fail on
x86.
gcc/cp/ChangeLog:
PR c++/88115
* cp-tree.h (cxx_sizeof_or_alignof_expr): Add bool parameter.
* decl.c (fold_sizeof_expr): Pass false to
cxx_sizeof_or_alignof_expr.
* parser.c (cp_parser_unary_expression): Pass std_alignof to
cxx_sizeof_or_alignof_expr.
* pt.c (tsubst_copy): Pass false to cxx_sizeof_or_alignof_expr.
(tsubst_copy_and_build): Pass std_alignof to
cxx_sizeof_or_alignof_expr.
* typeck.c (cxx_alignof_expr): Add std_alignof bool parameter
and pass it to cxx_sizeof_or_alignof_type. Set ALIGNOF_EXPR_STD_P
appropriately.
(cxx_sizeof_or_alignof_expr): Add std_alignof bool parameter
and pass it to cxx_alignof_expr. Assert op is either
SIZEOF_EXPR or ALIGNOF_EXPR.
libcc1/ChangeLog:
PR c++/88115
* libcp1plugin.cc (plugin_build_unary_expr): Pass true to
cxx_sizeof_or_alignof_expr.
gcc/testsuite/ChangeLog:
PR c++/88115
* g++.dg/cpp0x/alignof6.C: New test.
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
[not found] <bug-88115-4@http.gcc.gnu.org/bugzilla/>
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To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88115
--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:
https://gcc.gnu.org/g:b1c9b3c3408c1ec8043f9b9e1a148f84bb7f3b25
commit r11-4926-gb1c9b3c3408c1ec8043f9b9e1a148f84bb7f3b25
Author: Patrick Palka <ppalka@redhat.com>
Date: Wed Nov 11 15:11:23 2020 -0500
c++: Change the mangling of __alignof__ [PR88115]
This patch changes the mangling of __alignof__ to v111__alignof__,
making its mangling distinct from that of alignof(type) and
alignof(expr).
How we mangle ALIGNOF_EXPR now depends on its ALIGNOF_EXPR_STD_P flag,
which after the previous patch gets consistently set for alignof(type)
as well as alignof(expr).
gcc/c-family/ChangeLog:
PR c++/88115
* c-opts.c (c_common_post_options): Update latest_abi_version.
gcc/ChangeLog:
PR c++/88115
* common.opt (-fabi-version): Document =15.
* doc/invoke.texi (C++ Dialect Options): Likewise.
gcc/cp/ChangeLog:
PR c++/88115
* mangle.c (write_expression): Mangle __alignof_ differently
from alignof when the ABI version is at least 15.
libiberty/ChangeLog:
PR c++/88115
* cp-demangle.c (d_print_comp_inner)
<case DEMANGLE_COMPONENT_EXTENDED_OPERATOR>: Don't print the
"operator " prefix for __alignof__.
<case DEMANGLE_COMPONENT_UNARY>: Always print parens around the
operand of __alignof__.
* testsuite/demangle-expected: Test demangling for __alignof__.
gcc/testsuite/ChangeLog:
PR c++/88115
* g++.dg/abi/macro0.C: Adjust.
* g++.dg/cpp0x/alignof7.C: New test.
* g++.dg/cpp0x/alignof8.C: New test.
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
[not found] <bug-88115-4@http.gcc.gnu.org/bugzilla/>
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--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:
https://gcc.gnu.org/g:9df05884b3a30d32744a070d3fc5780b7323231a
commit r9-9043-g9df05884b3a30d32744a070d3fc5780b7323231a
Author: Patrick Palka <ppalka@redhat.com>
Date: Wed Oct 7 10:49:00 2020 -0400
c++: Distinguish alignof and __alignof__ in cp_tree_equal [PR97273]
cp_tree_equal currently considers alignof the same as __alignof__, but
these operators are semantically different ever since r8-7957. In the
testcase below, this causes the second static_assert to fail on targets
where alignof(double) != __alignof__(double) because the specialization
table (which uses cp_tree_equal as its equality predicate) conflates the
two dependent specializations integral_constant<__alignof__(T)> and
integral_constant<alignof(T)>.
This patch makes cp_tree_equal distinguish between these two operators
by inspecting the ALIGNOF_EXPR_STD_P flag.
gcc/cp/ChangeLog:
PR c++/88115
PR libstdc++/97273
* tree.c (cp_tree_equal) <case ALIGNOF_EXPR>: Return false if
ALIGNOF_EXPR_STD_P differ.
gcc/testsuite/ChangeLog:
PR c++/88115
PR libstdc++/97273
* g++.dg/template/alignof3.C: New test.
(cherry picked from commit 592fe221735bdaa375b1834dd49ce125d0b600d8)
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
[not found] <bug-88115-4@http.gcc.gnu.org/bugzilla/>
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To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88115
--- Comment #6 from James Y Knight <foom at fuhm dot net> ---
> c++: Change the mangling of __alignof__ [PR88115]
The new mangling chosen for __alignof__(type) seems problematic, and I think
this commit ought to be reverted until a new mangling scheme has been chosen.
At the very least, both __alignof__(expression) and __alignof__(type) can't
both be encoded as "v111__alignof__", with no indication of whether the
argument is a type or an expression, because that's ambiguous.
Possibly it'd be okay to use v112__alignof__z and v112__alignof__t, similar to
how "az" and "at" are used for standard alignof expression/type. That solves
the ambiguity. But -- this violates the generic grammar, which doesn't allow
for a vendor operator to take type arguments at all.
<operator-name> ::= v <digit> <source-name>
<expression> ::= <unary operator-name> <expression>
Now...possibly it's okay to violate that and pass a type, regardless. But, then
the demangler needs to know what every vendor extension operator's semantics
are in order to demangle -- which seems against the intent of the standardized
"vendor operator" syntax. So, that's not great.
This seems like a problem which may be worth solving properly and generally in
the itanium ABI -- maybe now's the time to actually do this? (Fixing this would
allow __typeof__, __builtin_convertvector, and __builtin_offsetof to be
mangleable too...) See also PR13740 and PR11078, for earlier (MUCH earlier!)
discussion of possible mangling syntax extensions for this sort of thing.
Unfortunately, it never went anywhere...
ISTM that the most promising proposal in those earlier threads was to add a "Y"
to both type and expression expansions.
To support vendor-specific builtins which returns a type, and can take types or
expressions as arguments (e.g. typeof), add:
<type> ::= Y <sourcename> <template-arg>+ E
To support vendor-specific builtins which return a value, and can take types or
expressions as arguments (e.g. __builtin_offsetof, or __alignof__):
<expression> ::= Y <sourcename> <template-arg>+ E
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
[not found] <bug-88115-4@http.gcc.gnu.org/bugzilla/>
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To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88115
--- Comment #7 from James Y Knight <foom at fuhm dot net> ---
I've created an ABI proposal against itanium abi, here:
https://github.com/itanium-cxx-abi/cxx-abi/issues/112
I realized since writing my last comment here that
<type> ::= u <source-name> [<template-args>] # vendor extended type
has been added a few months ago. Therefore, nothing needs to be added to
support extended expressions as <type>.
And, therefore, since 'u' is also free in expression, I've proposed to simply
add the same 'u' syntax to "expression", rather than using "Y", as per previous
comment.
That is:
<expression> ::= u <source-name> [<template-args>] # vendor extended
expression
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
[not found] <bug-88115-4@http.gcc.gnu.org/bugzilla/>
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--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Thanks for starting the discussion there.
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
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To: gcc-bugs
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--- Comment #9 from James Y Knight <foom at fuhm dot net> ---
Proposed patch posted for the itanium-cxx-abi:
https://github.com/itanium-cxx-abi/cxx-abi/pull/115/files
using the syntax:
u <source-name> <template-arg>* E
And to Clang, to use that syntax:
https://reviews.llvm.org/D93922
I hope both GCC and Clang can do the same thing here.
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
[not found] <bug-88115-4@http.gcc.gnu.org/bugzilla/>
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To: gcc-bugs
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--- Comment #10 from James Y Knight <foom at fuhm dot net> ---
Seeing as GCC is now in Stage 4 before the next release, I'd like to ping this
bug.
Should the priority be upgraded? I think fixing this so that GCC doesn't use
'v111__alignof__' should be considered a release-blocker: either the mangling
change should be reverted to the previous behavior, or fixed.
FWIW, the change to clang has been committed, and is planned to be in the
upcoming Clang 12 release
(https://reviews.llvm.org/rG9c7aeaebb3ac1b94200b59b111742cb6b8f090c2)
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
[not found] <bug-88115-4@http.gcc.gnu.org/bugzilla/>
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From: ppalka at gcc dot gnu.org @ 2021-02-01 14:16 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88115
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |ppalka at gcc dot gnu.org
CC| |ppalka at gcc dot gnu.org
--- Comment #11 from Patrick Palka <ppalka at gcc dot gnu.org> ---
(In reply to James Y Knight from comment #10)
> Seeing as GCC is now in Stage 4 before the next release, I'd like to ping
> this bug.
>
> Should the priority be upgraded? I think fixing this so that GCC doesn't use
> 'v111__alignof__' should be considered a release-blocker: either the
> mangling change should be reverted to the previous behavior, or fixed.
Yes, thanks for the ping. I'll work on a patch for GCC 11 to follow suit, so
that Clang and GCC do the same thing.
>
> FWIW, the change to clang has been committed, and is planned to be in the
> upcoming Clang 12 release
> (https://reviews.llvm.org/rG9c7aeaebb3ac1b94200b59b111742cb6b8f090c2)
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
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To: gcc-bugs
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--- Comment #12 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:
https://gcc.gnu.org/g:a3bf6ce7f2e17f2c977c13df23eb718e7b433dcd
commit r11-7921-ga3bf6ce7f2e17f2c977c13df23eb718e7b433dcd
Author: Patrick Palka <ppalka@redhat.com>
Date: Tue Mar 30 22:57:11 2021 -0400
c++: Adjust mangling of __alignof__ [PR88115]
r11-4926 made __alignof__ get mangled differently from alignof,
encoding __alignof__ as a vendor extended operator. But this
mangling is problematic for the reasons mentioned in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88115#c6.
This patch changes our mangling of __alignof__ to instead use the
new "vendor extended expression" syntax that's proposed in
https://github.com/itanium-cxx-abi/cxx-abi/issues/112. Clang does
the same thing already, so after this patch Clang and GCC agree
about the mangling of __alignof__(type) and __alignof__(expr).
gcc/cp/ChangeLog:
PR c++/88115
* mangle.c (write_expression): Adjust the mangling of
__alignof__.
include/ChangeLog:
PR c++/88115
* demangle.h (enum demangle_component_type): Add
DEMANGLE_COMPONENT_VENDOR_EXPR.
libiberty/ChangeLog:
PR c++/88115
* cp-demangle.c (d_dump, d_make_comp, d_expression_1)
(d_count_templates_scopes): Handle DEMANGLE_COMPONENT_VENDOR_EXPR.
(d_print_comp_inner): Likewise.
<case DEMANGLE_COMPONENT_EXTENDED_OPERATOR>: Revert r11-4926
change.
<case DEMANGLE_COMPONENT_UNARY>: Likewise.
* testsuite/demangle-expected: Adjust __alignof__ tests.
gcc/testsuite/ChangeLog:
PR c++/88115
* g++.dg/cpp0x/alignof7.C: Adjust expected mangling.
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
[not found] <bug-88115-4@http.gcc.gnu.org/bugzilla/>
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To: gcc-bugs
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--- Comment #13 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-8 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:
https://gcc.gnu.org/g:a34c19926b87f9cadd5ea84f5c5b93ae76b14558
commit r8-10855-ga34c19926b87f9cadd5ea84f5c5b93ae76b14558
Author: Patrick Palka <ppalka@redhat.com>
Date: Wed Oct 7 10:49:00 2020 -0400
c++: Distinguish alignof and __alignof__ in cp_tree_equal [PR97273]
cp_tree_equal currently considers alignof the same as __alignof__, but
these operators are semantically different ever since r8-7957. In the
testcase below, this causes the second static_assert to fail on targets
where alignof(double) != __alignof__(double) because the specialization
table (which uses cp_tree_equal as its equality predicate) conflates the
two dependent specializations integral_constant<__alignof__(T)> and
integral_constant<alignof(T)>.
This patch makes cp_tree_equal distinguish between these two operators
by inspecting the ALIGNOF_EXPR_STD_P flag.
gcc/cp/ChangeLog:
PR c++/88115
PR libstdc++/97273
* tree.c (cp_tree_equal) <case ALIGNOF_EXPR>: Return false if
ALIGNOF_EXPR_STD_P differ.
gcc/testsuite/ChangeLog:
PR c++/88115
PR libstdc++/97273
* g++.dg/template/alignof3.C: New test.
(cherry picked from commit 592fe221735bdaa375b1834dd49ce125d0b600d8)
^ permalink raw reply [flat|nested] 15+ messages in thread* [Bug c++/88115] Incorrect result from alignof in templates, if also using __alignof__.
[not found] <bug-88115-4@http.gcc.gnu.org/bugzilla/>
` (13 preceding siblings ...)
2021-04-21 12:08 ` cvs-commit at gcc dot gnu.org
@ 2021-04-21 12:10 ` ppalka at gcc dot gnu.org
14 siblings, 0 replies; 15+ messages in thread
From: ppalka at gcc dot gnu.org @ 2021-04-21 12:10 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88115
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|NEW |RESOLVED
Target Milestone|--- |8.5
--- Comment #14 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed.
^ permalink raw reply [flat|nested] 15+ messages in thread