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Application crash with debug symbols stripped out #39468

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dpelevin opened this issue Feb 2, 2017 · 7 comments
Closed

Application crash with debug symbols stripped out #39468

dpelevin opened this issue Feb 2, 2017 · 7 comments

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@dpelevin
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dpelevin commented Feb 2, 2017

With current implementation of the fix for #33985, application crashes in the case of panic, if debug info is stripped out with (strip -s helloworld.exe) and RUST_BACKTRACE is set to 1.

It can be reproduced with: beta-x86_64-pc-windows-gnu - rustc 1.16.0-beta.1 (5276ba7 2017-01-31)

@petrochenkov
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cc @segevfiner

@segevfiner
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segevfiner commented Feb 2, 2017

I tried building the following with rustc 1.16.0-beta.1 (5276ba72e 2017-01-31) (installed via rustup):

fn main() {
    println!("Hello, world!");
    panic!();
}

And stripped using strip -s from MSYS2 (up-to-date using pacman -Syu), in both debug and release, and it didn't crash for me. (Obviously printing "<unknown>" because the binary is stripped).

Don't you love those kind of crashes? 😝

@dpelevin Can you try and be more specific about what you did to cause this? Here are some ideas although they do sound a bit far fetched... Maybe someone else has a better idea.

  • Maybe it's dependent on your implementation of hello world?
  • Maybe it's your version of strip?
  • Maybe it's the linker used by rustc? (I think rustc always uses it's own bundled copy of gcc/ld on Windows regardless of PATH though)
  • Maybe PATH/rustup messed with you and it used some other rustc where the bug can be reproduced?

@petrochenkov
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Hm, I think I've reproduced it.

we@we-pc MINGW64 ~
$ cat test.rs
fn main() {
    println!("Hello, world!");
    panic!();
}

we@we-pc MINGW64 ~
$ rustc --version
rustc 1.16.0-nightly (24055d0f2 2017-01-31)

we@we-pc MINGW64 ~
$ rustc -g test.rs

we@we-pc MINGW64 ~
$ RUST_BACKTRACE=1 ./test.exe
Hello, world!
thread 'main' panicked at 'explicit panic', test.rs:3
stack backtrace:
   0:           0x4288ba - std::sys::imp::backtrace::_write::he5498b02db7db530
   1:           0x432f57 - std::panicking::default_hook::{{closure}}::h67a5fa5600945646
   2:           0x432b13 - std::panicking::default_hook::hf8a9629fab063fa5
   3:           0x4334de - std::panicking::rust_panic_with_hook::hf599e44aaa8545b8
   4:           0x4015d2 - std::panicking::begin_panic::h9a6bae97ed4f65b2
                        at C:\bot\slave\nightly-dist-rustc-win-gnu-64\build\src\libstd/panicking.rs:517
   5:           0x401871 - test::main::ha6bc039bc682a0db
                        at C:\msys64\home\we/test.rs:3
   6:           0x433168 - std::panicking::try::do_call::h4c4de3903bc7c076
   7:           0x43d178 - _rust_maybe_catch_panic
   8:           0x433c83 - std::rt::lang_start::h177832d72b1c79c7
   9:           0x4018aa - main
  10:           0x4013b4 - _tmainCRTStartup
  11:           0x4014e7 - mainCRTStartup
  12:     0x7ffc73cf13d1 - unit_addrs_search

we@we-pc MINGW64 ~
$ which strip
/c/mingw-w64/x86_64-6.2.0-win32-seh-rt_v5-rev1/mingw64/bin/strip

we@we-pc MINGW64 ~
$ strip ./test.exe

we@we-pc MINGW64 ~
$ RUST_BACKTRACE=1 ./test.exe
Hello, world!
thread 'main' panicked at 'explicit panic', test.rs:3
stack backtrace:

we@we-pc MINGW64 ~
$ RUST_BACKTRACE=1 gdb ./test.exe
GNU gdb (GDB) 7.9
Copyright (C) 2015 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-msys".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Traceback (most recent call last):
  File "<string>", line 3, in <module>
ImportError: No module named libstdcxx.v6.printers
/etc/gdbinit:6: Error in sourced command file:
Error while executing Python code.
Reading symbols from ./test.exe...(no debugging symbols found)...done.
(gdb) run
Starting program: /home/we/test.exe
[New Thread 6068.0x126c]
Hello, world!
thread 'main' panicked at 'explicit panic', test.rs:3
stack backtrace:
warning: Critical error detected c0000374

Program received signal SIGTRAP, Trace/breakpoint trap.
0x00007ffc74361b30 in ntdll!RtlpNtMakeTemporaryKey () from /c/Windows/SYSTEM32/ntdll.dll
(gdb) c
Continuing.
gdb: unknown target exception 0xc0000374 at 0x7ffc74361b70

Program received signal ?, Unknown signal.
0x00007ffc74361b70 in ntdll!RtlpNtMakeTemporaryKey () from /c/Windows/SYSTEM32/ntdll.dll
(gdb) c
Continuing.
[Inferior 1 (process 6068) exited with code 030000001564]
(gdb) q

@dpelevin
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dpelevin commented Feb 2, 2017

  1. Here is the HelloWorld I can reproduce problem with: https://github.com/dpelevin/helloworld

  2. I've uploaded strip.exe I was using: https://github.com/dpelevin/helloworld/tree/master/misc
    C:\MinGW\bin>strip.exe --version
    GNU strip (GNU Binutils) 2.24
    Copyright 2013 Free Software Foundation, Inc.
    This program is free software; you may redistribute it under the terms of
    the GNU General Public License version 3 or (at your option) any later version.
    This program has absolutely no warranty.

  3. I have the same MinGW version in the PATH as Rust uses:
    C:\MinGW\bin>ld.exe --version
    GNU ld (GNU Binutils) 2.24
    Copyright 2013 Free Software Foundation, Inc.
    This program is free software; you may redistribute it under the terms of
    the GNU General Public License version 3 or (at your option) a later version.
    This program has absolutely no warranty.
    C:\MinGW\bin>gcc.exe --version
    gcc.exe (x86_64-posix-seh-rev3, Built by MinGW-W64 project) 4.9.1
    Copyright (C) 2014 Free Software Foundation, Inc.
    This is free software; see the source for copying conditions. There is NO
    warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Additionally I've renamed C:\MinGW to C:\MinGW_ to remove it from PATH and the problem were still in place.

  1. I've tried to reinstall beta version:
    rustup toolchain remove beta-x86_64-pc-windows-gnu
    ...
    rustup toolchain install beta-x86_64-pc-windows-gnu
    ....
    beta-x86_64-pc-windows-gnu installed - rustc 1.16.0-beta.1 (5276ba7 2017-01-31)
    rustup default beta-gnu
    ...
    beta-x86_64-pc-windows-gnu unchanged - rustc 1.16.0-beta.1 (5276ba7 2017-01-31)

Still crashes.

UPD: Look like you've already caught it :)

@segevfiner
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@petrochenkov
It looks like heap corruption (STATUS_HEAP_CORRUPTION - 0xC0000374)
You can try application verifier on the executable (Win+R appverif.exe if you have some Windows SDK installed), it is often able to break on the error exactly , but I'm not sure how well it works with GNU stuff.

Sadly it still doesn't reproduce on my machine, so I can't debug myself. 😞
Some other stuff I can think of that might be the reason why it doesn't reproduce on my computer:
I'm on Windows 10.0.14393.693 64-bit
I don't have any dbghelp.dll on PATH besides the one in C:\Windows\System32

@petrochenkov
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Usual free(uninitialized_pointer), move along, nothing to see here.
Fixed in #39509

@brson
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brson commented Feb 3, 2017

cc @fitzgen libbacktrace crash

frewsxcv added a commit to frewsxcv/rust that referenced this issue Feb 5, 2017
frewsxcv added a commit to frewsxcv/rust that referenced this issue Feb 5, 2017
frewsxcv added a commit to frewsxcv/rust that referenced this issue Feb 5, 2017
alexcrichton added a commit to alexcrichton/libbacktrace that referenced this issue Jul 25, 2017
In rust-lang/rust#39468 it was discovered that this could cause a crash in
libbacktrace due to freeing uninitialized memory, and this specific instance was
fixed in rust-lang/rust#39509
alexcrichton added a commit to alexcrichton/rust that referenced this issue Jul 17, 2020
This commit is a proof-of-concept for switching the standard library's
backtrace symbolication mechanism on most platforms from libbacktrace to
gimli. The standard library's support for `RUST_BACKTRACE=1` requires
in-process parsing of object files and DWARF debug information to
interpret it and print the filename/line number of stack frames as part
of a backtrace.

Historically this support in the standard library has come from a
library called "libbacktrace". The libbacktrace library seems to have
been extracted from gcc at some point and is written in C. We've had a
lot of issues with libbacktrace over time, unfortunately, though. The
library does not appear to be actively maintained since we've had
patches sit for months-to-years without comments. We have discovered a
good number of soundness issues with the library itself, both when
parsing valid DWARF as well as invalid DWARF. This is enough of an issue
that the libs team has previously decided that we cannot feed untrusted
inputs to libbacktrace. This also doesn't take into account the
portability of libbacktrace which has been difficult to manage and
maintain over time. While possible there are lots of exceptions and it's
the main C dependency of the standard library right now.

For years it's been the desire to switch over to a Rust-based solution
for symbolicating backtraces. It's been assumed that we'll be using the
Gimli family of crates for this purpose, which are targeted at safely
and efficiently parsing DWARF debug information. I've been working
recently to shore up the Gimli support in the `backtrace` crate. As of a
few weeks ago the `backtrace` crate, by default, uses Gimli when loaded
from crates.io. This transition has gone well enough that I figured it
was time to start talking seriously about this change to the standard
library.

This commit is a preview of what's probably the best way to integrate
the `backtrace` crate into the standard library with the Gimli feature
turned on. While today it's used as a crates.io dependency, this commit
switches the `backtrace` crate to a submodule of this repository which
will need to be updated manually. This is not done lightly, but is
thought to be the best solution. The primary reason for this is that the
`backtrace` crate needs to do some pretty nontrivial filesystem
interactions to locate debug information. Working without `std::fs` is
not an option, and while it might be possible to do some sort of
trait-based solution when prototyped it was found to be too unergonomic.
Using a submodule allows the `backtrace` crate to build as a submodule
of the `std` crate itself, enabling it to use `std::fs` and such.

Otherwise this adds new dependencies to the standard library. This step
requires extra attention because this means that these crates are now
going to be included with all Rust programs by default. It's important
to note, however, that we're already shipping libbacktrace with all Rust
programs by default and it has a bunch of C code implementing all of
this internally anyway, so we're basically already switching
already-shipping functionality to Rust from C.

* `object` - this crate is used to parse object file headers and
  contents. Very low-level support is used from this crate and almost
  all of it is disabled. Largely we're just using struct definitions as
  well as convenience methods internally to read bytes and such.

* `addr2line` - this is the main meat of the implementation for
  symbolication. This crate depends on `gimli` for DWARF parsing and
  then provides interfaces needed by the `backtrace` crate to turn an
  address into a filename / line number. This crate is actually pretty
  small (fits in a single file almost!) and mirrors most of what
  `dwarf.c` does for libbacktrace.

* `miniz_oxide` - the libbacktrace crate transparently handles
  compressed debug information which is compressed with zlib. This crate
  is used to decompress compressed debug sections.

* `gimli` - not actually used directly, but a dependency of `addr2line`.

* `adler32`- not used directly either, but a dependency of
  `miniz_oxide`.

The goal of this change is to improve the safety of backtrace
symbolication in the standard library, especially in the face of
possibly malformed DWARF debug information. Even to this day we're still
seeing segfaults in libbacktrace which could possibly become security
vulnerabilities. This change should almost entirely eliminate this
possibility whilc also paving the way forward to adding more features
like split debug information.

Some references for those interested are:

* Original addition of libbacktrace - rust-lang#12602
* OOM with libbacktrace - rust-lang#24231
* Backtrace failure due to use of uninitialized value - rust-lang#28447
* Possibility to feed untrusted data to libbacktrace - rust-lang#21889
* Soundness fix for libbacktrace - rust-lang#33729
* Crash in libbacktrace - rust-lang#39468
* Support for macOS, never merged - ianlancetaylor/libbacktrace#2
* Performance issues with libbacktrace - rust-lang#29293, rust-lang#37477
* Update procedure is quite complicated due to how many patches we
  need to carry - rust-lang#50955
* Libbacktrace doesn't work on MinGW with dynamic libs - rust-lang#71060
* Segfault in libbacktrace on macOS - rust-lang#71397

Switching to Rust will not make us immune to all of these issues. The
crashes are expected to go away, but correctness and performance may
still have bugs arise. The gimli and `backtrace` crates, however, are
actively maintained unlike libbacktrace, so this should enable us to at
least efficiently apply fixes as situations come up.
bors added a commit to rust-lang-ci/rust that referenced this issue Jul 18, 2020
…Simulacrum

std: Switch from libbacktrace to gimli

This commit is a proof-of-concept for switching the standard library's
backtrace symbolication mechanism on most platforms from libbacktrace to
gimli. The standard library's support for `RUST_BACKTRACE=1` requires
in-process parsing of object files and DWARF debug information to
interpret it and print the filename/line number of stack frames as part
of a backtrace.

Historically this support in the standard library has come from a
library called "libbacktrace". The libbacktrace library seems to have
been extracted from gcc at some point and is written in C. We've had a
lot of issues with libbacktrace over time, unfortunately, though. The
library does not appear to be actively maintained since we've had
patches sit for months-to-years without comments. We have discovered a
good number of soundness issues with the library itself, both when
parsing valid DWARF as well as invalid DWARF. This is enough of an issue
that the libs team has previously decided that we cannot feed untrusted
inputs to libbacktrace. This also doesn't take into account the
portability of libbacktrace which has been difficult to manage and
maintain over time. While possible there are lots of exceptions and it's
the main C dependency of the standard library right now.

For years it's been the desire to switch over to a Rust-based solution
for symbolicating backtraces. It's been assumed that we'll be using the
Gimli family of crates for this purpose, which are targeted at safely
and efficiently parsing DWARF debug information. I've been working
recently to shore up the Gimli support in the `backtrace` crate. As of a
few weeks ago the `backtrace` crate, by default, uses Gimli when loaded
from crates.io. This transition has gone well enough that I figured it
was time to start talking seriously about this change to the standard
library.

This commit is a preview of what's probably the best way to integrate
the `backtrace` crate into the standard library with the Gimli feature
turned on. While today it's used as a crates.io dependency, this commit
switches the `backtrace` crate to a submodule of this repository which
will need to be updated manually. This is not done lightly, but is
thought to be the best solution. The primary reason for this is that the
`backtrace` crate needs to do some pretty nontrivial filesystem
interactions to locate debug information. Working without `std::fs` is
not an option, and while it might be possible to do some sort of
trait-based solution when prototyped it was found to be too unergonomic.
Using a submodule allows the `backtrace` crate to build as a submodule
of the `std` crate itself, enabling it to use `std::fs` and such.

Otherwise this adds new dependencies to the standard library. This step
requires extra attention because this means that these crates are now
going to be included with all Rust programs by default. It's important
to note, however, that we're already shipping libbacktrace with all Rust
programs by default and it has a bunch of C code implementing all of
this internally anyway, so we're basically already switching
already-shipping functionality to Rust from C.

* `object` - this crate is used to parse object file headers and
  contents. Very low-level support is used from this crate and almost
  all of it is disabled. Largely we're just using struct definitions as
  well as convenience methods internally to read bytes and such.

* `addr2line` - this is the main meat of the implementation for
  symbolication. This crate depends on `gimli` for DWARF parsing and
  then provides interfaces needed by the `backtrace` crate to turn an
  address into a filename / line number. This crate is actually pretty
  small (fits in a single file almost!) and mirrors most of what
  `dwarf.c` does for libbacktrace.

* `miniz_oxide` - the libbacktrace crate transparently handles
  compressed debug information which is compressed with zlib. This crate
  is used to decompress compressed debug sections.

* `gimli` - not actually used directly, but a dependency of `addr2line`.

* `adler32`- not used directly either, but a dependency of
  `miniz_oxide`.

The goal of this change is to improve the safety of backtrace
symbolication in the standard library, especially in the face of
possibly malformed DWARF debug information. Even to this day we're still
seeing segfaults in libbacktrace which could possibly become security
vulnerabilities. This change should almost entirely eliminate this
possibility whilc also paving the way forward to adding more features
like split debug information.

Some references for those interested are:

* Original addition of libbacktrace - rust-lang#12602
* OOM with libbacktrace - rust-lang#24231
* Backtrace failure due to use of uninitialized value - rust-lang#28447
* Possibility to feed untrusted data to libbacktrace - rust-lang#21889
* Soundness fix for libbacktrace - rust-lang#33729
* Crash in libbacktrace - rust-lang#39468
* Support for macOS, never merged - ianlancetaylor/libbacktrace#2
* Performance issues with libbacktrace - rust-lang#29293, rust-lang#37477
* Update procedure is quite complicated due to how many patches we
  need to carry - rust-lang#50955
* Libbacktrace doesn't work on MinGW with dynamic libs - rust-lang#71060
* Segfault in libbacktrace on macOS - rust-lang#71397

Switching to Rust will not make us immune to all of these issues. The
crashes are expected to go away, but correctness and performance may
still have bugs arise. The gimli and `backtrace` crates, however, are
actively maintained unlike libbacktrace, so this should enable us to at
least efficiently apply fixes as situations come up.

---

I want to note that my purpose for creating a PR here is to start a conversation about this. I think that all the various pieces are in place that this is compelling enough that I think this transition should be talked about seriously. There are a number of items which still need to be addressed before actually merging this PR, however:

* [ ] `gimli` needs to be published to crates.io
* [ ] `addr2line` needs a publish
* [ ] `miniz_oxide` needs a publish
* [ ] Tests probably shouldn't recommend the `gimli` crate's traits for implementing
* [ ] The `backtrace` crate's branch changes need to be merged to the master branch (rust-lang/backtrace-rs#349)
* [ ] The support for `libbacktrace` on some platforms needs to be audited to see if we should support more strategies in the gimli implementation - rust-lang/backtrace-rs#325, rust-lang/backtrace-rs#326, rust-lang/backtrace-rs#350, rust-lang/backtrace-rs#351

Most of the merging/publishing I'm not actively pushing on right now. It's a bit wonky for crates to support libstd so I'm holding off on pulling the trigger everywhere until there's a bit more discussion about how to go through with this. Namely rust-lang/backtrace-rs#349 I'm going to hold off merging until we decide to go through with the submodule strategy.

In any case this is a pretty major change, so I suspect that the compiler team is likely going to be interested in this. I don't mean to force changes by dumping a bunch of code by any means. Integration of external crates into the standard library is so difficult I wanted to have a proof-of-concept to review while talking about whether to do this at all (hence the PR), but I'm more than happy to follow any processes needed to merge this. I must admit though that I'm not entirely sure myself at this time what the process would be to decide to merge this, so I'm hoping others can help me figure that out!
alexcrichton added a commit to alexcrichton/rust that referenced this issue Jul 28, 2020
This commit is a proof-of-concept for switching the standard library's
backtrace symbolication mechanism on most platforms from libbacktrace to
gimli. The standard library's support for `RUST_BACKTRACE=1` requires
in-process parsing of object files and DWARF debug information to
interpret it and print the filename/line number of stack frames as part
of a backtrace.

Historically this support in the standard library has come from a
library called "libbacktrace". The libbacktrace library seems to have
been extracted from gcc at some point and is written in C. We've had a
lot of issues with libbacktrace over time, unfortunately, though. The
library does not appear to be actively maintained since we've had
patches sit for months-to-years without comments. We have discovered a
good number of soundness issues with the library itself, both when
parsing valid DWARF as well as invalid DWARF. This is enough of an issue
that the libs team has previously decided that we cannot feed untrusted
inputs to libbacktrace. This also doesn't take into account the
portability of libbacktrace which has been difficult to manage and
maintain over time. While possible there are lots of exceptions and it's
the main C dependency of the standard library right now.

For years it's been the desire to switch over to a Rust-based solution
for symbolicating backtraces. It's been assumed that we'll be using the
Gimli family of crates for this purpose, which are targeted at safely
and efficiently parsing DWARF debug information. I've been working
recently to shore up the Gimli support in the `backtrace` crate. As of a
few weeks ago the `backtrace` crate, by default, uses Gimli when loaded
from crates.io. This transition has gone well enough that I figured it
was time to start talking seriously about this change to the standard
library.

This commit is a preview of what's probably the best way to integrate
the `backtrace` crate into the standard library with the Gimli feature
turned on. While today it's used as a crates.io dependency, this commit
switches the `backtrace` crate to a submodule of this repository which
will need to be updated manually. This is not done lightly, but is
thought to be the best solution. The primary reason for this is that the
`backtrace` crate needs to do some pretty nontrivial filesystem
interactions to locate debug information. Working without `std::fs` is
not an option, and while it might be possible to do some sort of
trait-based solution when prototyped it was found to be too unergonomic.
Using a submodule allows the `backtrace` crate to build as a submodule
of the `std` crate itself, enabling it to use `std::fs` and such.

Otherwise this adds new dependencies to the standard library. This step
requires extra attention because this means that these crates are now
going to be included with all Rust programs by default. It's important
to note, however, that we're already shipping libbacktrace with all Rust
programs by default and it has a bunch of C code implementing all of
this internally anyway, so we're basically already switching
already-shipping functionality to Rust from C.

* `object` - this crate is used to parse object file headers and
  contents. Very low-level support is used from this crate and almost
  all of it is disabled. Largely we're just using struct definitions as
  well as convenience methods internally to read bytes and such.

* `addr2line` - this is the main meat of the implementation for
  symbolication. This crate depends on `gimli` for DWARF parsing and
  then provides interfaces needed by the `backtrace` crate to turn an
  address into a filename / line number. This crate is actually pretty
  small (fits in a single file almost!) and mirrors most of what
  `dwarf.c` does for libbacktrace.

* `miniz_oxide` - the libbacktrace crate transparently handles
  compressed debug information which is compressed with zlib. This crate
  is used to decompress compressed debug sections.

* `gimli` - not actually used directly, but a dependency of `addr2line`.

* `adler32`- not used directly either, but a dependency of
  `miniz_oxide`.

The goal of this change is to improve the safety of backtrace
symbolication in the standard library, especially in the face of
possibly malformed DWARF debug information. Even to this day we're still
seeing segfaults in libbacktrace which could possibly become security
vulnerabilities. This change should almost entirely eliminate this
possibility whilc also paving the way forward to adding more features
like split debug information.

Some references for those interested are:

* Original addition of libbacktrace - rust-lang#12602
* OOM with libbacktrace - rust-lang#24231
* Backtrace failure due to use of uninitialized value - rust-lang#28447
* Possibility to feed untrusted data to libbacktrace - rust-lang#21889
* Soundness fix for libbacktrace - rust-lang#33729
* Crash in libbacktrace - rust-lang#39468
* Support for macOS, never merged - ianlancetaylor/libbacktrace#2
* Performance issues with libbacktrace - rust-lang#29293, rust-lang#37477
* Update procedure is quite complicated due to how many patches we
  need to carry - rust-lang#50955
* Libbacktrace doesn't work on MinGW with dynamic libs - rust-lang#71060
* Segfault in libbacktrace on macOS - rust-lang#71397

Switching to Rust will not make us immune to all of these issues. The
crashes are expected to go away, but correctness and performance may
still have bugs arise. The gimli and `backtrace` crates, however, are
actively maintained unlike libbacktrace, so this should enable us to at
least efficiently apply fixes as situations come up.
dscho pushed a commit to dscho/libbacktrace that referenced this issue Jul 18, 2022
In rust-lang/rust#39468 it was discovered that this could cause a crash in
libbacktrace due to freeing uninitialized memory, and this specific instance was
fixed in rust-lang/rust#39509
johnsonjh added a commit to johnsonjh/libbacktrace that referenced this issue Oct 18, 2022
… of uninitialized bytes in pecoff.c; 3) Fix a use of undefined memory in pecoff.c

1) Note: as we target MINGW here, we still want to look up the symbols via
the DWARF method (the native Windows way would be to call the
SymFromAddr() function, but that would require .pdb files which MINGW
does not produce).
Signed-off-by: Johannes Schindelin <[email protected]>

2) This updates the local declaration of `str_size` to always be 4 bytes instead of
platform-dependent as its initialization later on only fills in 4 bytes instead
of all the bytes of `size_t`.
Originally reported as rust-lang/rust#28447 this was fixed in
rust-lang/rust#30908

3) In rust-lang/rust#39468 it was discovered that this could cause a crash in
libbacktrace due to freeing uninitialized memory, and this specific instance was
fixed in rust-lang/rust#39509
dscho pushed a commit to dscho/libbacktrace that referenced this issue Apr 8, 2024
In rust-lang/rust#39468 it was discovered that this could cause a crash in
libbacktrace due to freeing uninitialized memory, and this specific instance was
fixed in rust-lang/rust#39509
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