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* [Bug gdb/27059] New: gdb.fortran/vla-type.exp fails when GDB is built with ASan
@ 2020-12-13 0:50 simark at simark dot ca
2020-12-13 0:50 ` [Bug gdb/27059] " simark at simark dot ca
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: simark at simark dot ca @ 2020-12-13 0:50 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=27059
Bug ID: 27059
Summary: gdb.fortran/vla-type.exp fails when GDB is built with
ASan
Product: gdb
Version: HEAD
Status: NEW
Severity: normal
Priority: P2
Component: gdb
Assignee: unassigned at sourceware dot org
Reporter: simark at simark dot ca
Target Milestone: ---
Since 5bbd8269fa8d ("gdb/fortran: array stride support"), the test
gdb.fortran/vla-type.exp fails when GDB is built with AddressSanitizer.
This is the failure:
ptype fivedynarr(2)
/home/simark/src/binutils-gdb/gdb/valarith.c:1390:10: runtime error: signed
integer overflow: 3573412791104 * 140737350904416 cannot be represented in type
'long int'
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* [Bug gdb/27059] gdb.fortran/vla-type.exp fails when GDB is built with ASan
2020-12-13 0:50 [Bug gdb/27059] New: gdb.fortran/vla-type.exp fails when GDB is built with ASan simark at simark dot ca
@ 2020-12-13 0:50 ` simark at simark dot ca
2020-12-24 16:46 ` cvs-commit at gcc dot gnu.org
2020-12-24 16:48 ` andrew.burgess at embecosm dot com
2 siblings, 0 replies; 4+ messages in thread
From: simark at simark dot ca @ 2020-12-13 0:50 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=27059
Simon Marchi <simark at simark dot ca> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |11.1
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* [Bug gdb/27059] gdb.fortran/vla-type.exp fails when GDB is built with ASan
2020-12-13 0:50 [Bug gdb/27059] New: gdb.fortran/vla-type.exp fails when GDB is built with ASan simark at simark dot ca
2020-12-13 0:50 ` [Bug gdb/27059] " simark at simark dot ca
@ 2020-12-24 16:46 ` cvs-commit at gcc dot gnu.org
2020-12-24 16:48 ` andrew.burgess at embecosm dot com
2 siblings, 0 replies; 4+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2020-12-24 16:46 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=27059
--- Comment #1 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Andrew Burgess <aburgess@sourceware.org>:
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=b7874836c331d13e5478c775477b12abf7c481a0
commit b7874836c331d13e5478c775477b12abf7c481a0
Author: Andrew Burgess <andrew.burgess@embecosm.com>
Date: Fri Dec 18 11:59:54 2020 +0000
gdb: avoid resolving dynamic properties for non-allocated arrays
In PR gdb/27059 an issue was discovered where GDB would sometimes
trigger undefined behaviour in the form of signed integer overflow.
The problem here is that GDB was reading random garbage from the
inferior memory space, assuming this data was valid, and performing
arithmetic on it.
This bug raises an interesting general problem with GDB's DWARF
expression evaluator, which is this:
We currently assume that the DWARF expressions being evaluated are
well formed, and well behaving. As an example, this is the expression
that the bug was running into problems on, this was used as the
expression for a DW_AT_byte_stride of a DW_TAG_subrange_type:
DW_OP_push_object_address;
DW_OP_plus_uconst: 88;
DW_OP_deref;
DW_OP_push_object_address;
DW_OP_plus_uconst: 32;
DW_OP_deref;
DW_OP_mul
Two values are read from the inferior and multiplied together. GDB
should not assume that any value read from the inferior is in any way
sane, as such the implementation of DW_OP_mul should be guarding
against overflow and doing something semi-sane here.
However, it turns out that the original bug PR gdb/27059, is hitting a
more specific case, which doesn't require changes to the DWARF
expression evaluator, so I'm going to leave the above issue for
another day.
In the test mentioned in the bug GDB is actually trying to resolve the
dynamic type of a Fortran array that is NOT allocated. A
non-allocated Fortran array is one that does not have any data
allocated for it yet, and even the upper and lower bounds of the array
are not yet known.
It turns out that, at least for gfortran compiled code, the data
fields that describe the byte-stride are not initialised until the
array is allocated.
This leads me to the following conclusion: GDB should not try to
resolve the bounds, or stride information for an array that is not
allocated (or not associated, a similar, but slightly different
Fortran feature). Instead, each of these properties should be set to
undefined if the array is not allocated (or associated).
That is what this commit does. There's a new flag that is passed
around during the dynamic array resolution. When this flag is true
the dynamic properties are resolved using the DWARF expressions as
they currently are, but when this flag is false the expressions are
not evaluated, and instead the properties are set to undefined.
gdb/ChangeLog:
PR gdb/27059
* eval.c (evaluate_subexp_for_sizeof): Handle not allocated and
not associated arrays.
* f-lang.c (fortran_adjust_dynamic_array_base_address_hack): Don't
adjust arrays that are not allocated/associated.
* gdbtypes.c (resolve_dynamic_range): Update header comment. Add
new parameter which is used to sometimes set dynamic properties to
undefined.
(resolve_dynamic_array_or_string): Update header comment. Add new
parameter which is used to guard evaluating dynamic properties.
Resolve allocated/associated properties first.
gdb/testsuite/ChangeLog:
PR gdb/27059
* gdb.dwarf2/dyn-type-unallocated.c: New file.
* gdb.dwarf2/dyn-type-unallocated.exp: New file.
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* [Bug gdb/27059] gdb.fortran/vla-type.exp fails when GDB is built with ASan
2020-12-13 0:50 [Bug gdb/27059] New: gdb.fortran/vla-type.exp fails when GDB is built with ASan simark at simark dot ca
2020-12-13 0:50 ` [Bug gdb/27059] " simark at simark dot ca
2020-12-24 16:46 ` cvs-commit at gcc dot gnu.org
@ 2020-12-24 16:48 ` andrew.burgess at embecosm dot com
2 siblings, 0 replies; 4+ messages in thread
From: andrew.burgess at embecosm dot com @ 2020-12-24 16:48 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=27059
Andrew Burgess <andrew.burgess at embecosm dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|NEW |RESOLVED
CC| |andrew.burgess at embecosm dot com
--- Comment #2 from Andrew Burgess <andrew.burgess at embecosm dot com> ---
This issue should now be resolved.
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2020-12-13 0:50 [Bug gdb/27059] New: gdb.fortran/vla-type.exp fails when GDB is built with ASan simark at simark dot ca
2020-12-13 0:50 ` [Bug gdb/27059] " simark at simark dot ca
2020-12-24 16:46 ` cvs-commit at gcc dot gnu.org
2020-12-24 16:48 ` andrew.burgess at embecosm dot com
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