* [Bug default/26739] New: Handle qualified typedef array types
@ 2020-10-15 18:21 gprocida+abigail at google dot com
2020-10-23 16:36 ` [Bug default/26739] " dodji at redhat dot com
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: gprocida+abigail at google dot com @ 2020-10-15 18:21 UTC (permalink / raw)
To: libabigail
https://sourceware.org/bugzilla/show_bug.cgi?id=26739
Bug ID: 26739
Summary: Handle qualified typedef array types
Product: libabigail
Version: unspecified
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: default
Assignee: dodji at redhat dot com
Reporter: gprocida+abigail at google dot com
CC: libabigail at sourceware dot org
Target Milestone: ---
The C language has a "feature" I believe also inherited by C++.
Array and function types cannot be CV-qualified. You can try with typedefs and
results are... non-obvious. Typedefs are *not* simply aliases.
If a typedef is qualified and it refers to a function type, then undefined
behaviour ensues. (WAT? Not legal, not illegal, not implementation-defined...
undefined.)
If a typedef is qualified and it refers to an array type, then the qualified
typedef resolves not necessarily to the original array type, but to a similar
one where the element types gain the qualifiers on the typedef. (WAT?!)
This means building C types requires a degree of evaluation rather than just
plain construction.
Unsurprisingly, this is confusing both to humans and to libabigail. The code
below has no ABI change, as member q is const int[7] in both versions. However,
abidiff reports things which may or may not be strictly true.
It's quite possible that the DWARF for these mutant typedefs is "interesting"
and I wouldn't be surprised if GCC and Clang have differences here. (GCC
already copies element type qualifiers to the array types, Clang does not).
==> mutant_typedef_arrays_c.0.c <==
typedef const int immutable[7];
typedef immutable monster;
struct A {
monster q;
};
void fun(struct A * a) { (void) a; }
==> mutant_typedef_arrays_c.1.c <==
typedef int plain[7];
typedef const plain monster;
struct A {
monster q;
};
void fun(struct A * a) {
(void) a;
// assignment to read-only location
// a->q[0] = 0;
}
$ abidiff --no-show-locs mutant_typedef_arrays_c.?.o
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C] 'function void fun(A*)' has some indirect sub-type changes:
parameter 1 of type 'A*' has sub-type changes:
in pointed to type 'struct A':
type size hasn't changed
1 data member change:
type of 'const monster A::q' changed:
in unqualified underlying type 'typedef monster':
underlying type 'typedef immutable' changed:
entity changed from 'typedef immutable' to compatible type
'int[7]'
array element type 'const int' changed:
entity changed from 'const int' to 'int'
type size hasn't changed
type name changed from 'const int[7]' to 'int[7]'
type size hasn't changed
$ echo $?
4
--
You are receiving this mail because:
You are on the CC list for the bug.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug default/26739] Handle qualified typedef array types
2020-10-15 18:21 [Bug default/26739] New: Handle qualified typedef array types gprocida+abigail at google dot com
@ 2020-10-23 16:36 ` dodji at redhat dot com
2020-10-27 17:22 ` dodji at redhat dot com
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: dodji at redhat dot com @ 2020-10-23 16:36 UTC (permalink / raw)
To: libabigail
https://sourceware.org/bugzilla/show_bug.cgi?id=26739
dodji at redhat dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Ever confirmed|0 |1
Last reconfirmed| |2020-10-23
--
You are receiving this mail because:
You are on the CC list for the bug.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug default/26739] Handle qualified typedef array types
2020-10-15 18:21 [Bug default/26739] New: Handle qualified typedef array types gprocida+abigail at google dot com
2020-10-23 16:36 ` [Bug default/26739] " dodji at redhat dot com
@ 2020-10-27 17:22 ` dodji at redhat dot com
2020-11-09 14:35 ` dodji at redhat dot com
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: dodji at redhat dot com @ 2020-10-27 17:22 UTC (permalink / raw)
To: libabigail
https://sourceware.org/bugzilla/show_bug.cgi?id=26739
--- Comment #1 from dodji at redhat dot com ---
Thank you for taking the time to report this problem.
I posted a patch (for review) to the mailing list that should hopefully handle
this issue.
It can be read at
https://sourceware.org/pipermail/libabigail/2020q4/002779.html.
--
You are receiving this mail because:
You are on the CC list for the bug.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug default/26739] Handle qualified typedef array types
2020-10-15 18:21 [Bug default/26739] New: Handle qualified typedef array types gprocida+abigail at google dot com
2020-10-23 16:36 ` [Bug default/26739] " dodji at redhat dot com
2020-10-27 17:22 ` dodji at redhat dot com
@ 2020-11-09 14:35 ` dodji at redhat dot com
2020-11-09 14:35 ` dodji at redhat dot com
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: dodji at redhat dot com @ 2020-11-09 14:35 UTC (permalink / raw)
To: libabigail
https://sourceware.org/bugzilla/show_bug.cgi?id=26739
--- Comment #2 from dodji at redhat dot com ---
I posted an updated patch at html
--
You are receiving this mail because:
You are on the CC list for the bug.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug default/26739] Handle qualified typedef array types
2020-10-15 18:21 [Bug default/26739] New: Handle qualified typedef array types gprocida+abigail at google dot com
` (2 preceding siblings ...)
2020-11-09 14:35 ` dodji at redhat dot com
@ 2020-11-09 14:35 ` dodji at redhat dot com
2020-11-13 17:10 ` dodji at redhat dot com
2020-12-04 17:09 ` gprocida+abigail at google dot com
5 siblings, 0 replies; 7+ messages in thread
From: dodji at redhat dot com @ 2020-11-09 14:35 UTC (permalink / raw)
To: libabigail
https://sourceware.org/bugzilla/show_bug.cgi?id=26739
--- Comment #3 from dodji at redhat dot com ---
Sorry, I meant I posted an updated patch at
https://sourceware.org/pipermail/libabigail/2020q4/002810.html
--
You are receiving this mail because:
You are on the CC list for the bug.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug default/26739] Handle qualified typedef array types
2020-10-15 18:21 [Bug default/26739] New: Handle qualified typedef array types gprocida+abigail at google dot com
` (3 preceding siblings ...)
2020-11-09 14:35 ` dodji at redhat dot com
@ 2020-11-13 17:10 ` dodji at redhat dot com
2020-12-04 17:09 ` gprocida+abigail at google dot com
5 siblings, 0 replies; 7+ messages in thread
From: dodji at redhat dot com @ 2020-11-13 17:10 UTC (permalink / raw)
To: libabigail
https://sourceware.org/bugzilla/show_bug.cgi?id=26739
dodji at redhat dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |NOTABUG
Status|ASSIGNED |RESOLVED
--- Comment #4 from dodji at redhat dot com ---
This one has been committed at
https://sourceware.org/git/?p=libabigail.git;a=commit;h=3c87247cb42a3d3d8f57b02ded34c35284aea51a
and should be available in libabigail 1.8.
Thanks for taking the time to report this problem!
--
You are receiving this mail because:
You are on the CC list for the bug.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug default/26739] Handle qualified typedef array types
2020-10-15 18:21 [Bug default/26739] New: Handle qualified typedef array types gprocida+abigail at google dot com
` (4 preceding siblings ...)
2020-11-13 17:10 ` dodji at redhat dot com
@ 2020-12-04 17:09 ` gprocida+abigail at google dot com
5 siblings, 0 replies; 7+ messages in thread
From: gprocida+abigail at google dot com @ 2020-12-04 17:09 UTC (permalink / raw)
To: libabigail
https://sourceware.org/bugzilla/show_bug.cgi?id=26739
Giuliano Procida <gprocida+abigail at google dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|NOTABUG |---
--- Comment #5 from Giuliano Procida <gprocida+abigail at google dot com> ---
Hi Dodji.
Please take a look at
https://sourceware.org/pipermail/libabigail/2020q4/002992.html. I used GCC
10.2.0.
This is actually a test case I came up with to exercise BTF (pahole / libbtf).
This is an area where, until we check and verify otherwise, no part of the
toolchain should be beyond suspicion.
However, we are definitely seeing some incorrect reporting here.
--
You are receiving this mail because:
You are on the CC list for the bug.
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2020-12-04 17:09 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-10-15 18:21 [Bug default/26739] New: Handle qualified typedef array types gprocida+abigail at google dot com
2020-10-23 16:36 ` [Bug default/26739] " dodji at redhat dot com
2020-10-27 17:22 ` dodji at redhat dot com
2020-11-09 14:35 ` dodji at redhat dot com
2020-11-09 14:35 ` dodji at redhat dot com
2020-11-13 17:10 ` dodji at redhat dot com
2020-12-04 17:09 ` gprocida+abigail at google dot com
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).