[ruby-core:103672] [Ruby master Bug#17810] addr2line.c: Some symbol names missing in C backtrace with Clang/LLVM

Issue #17810 has been updated by xtkoba (Tee KOBAYASHI).


PR: https://github.com/ruby/ruby/pull/4438

The second patch is omitted from the PR, because it turns out to be not very useful. The corresponding source file name should be easily guessable from the symbol name.

----------------------------------------
Bug #17810: addr2line.c: Some symbol names missing in C backtrace with Clang/LLVM
https://bugs.ruby-lang.org/issues/17810#change-91767

* Author: xtkoba (Tee KOBAYASHI)
* Status: Open
* Priority: Normal
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
When Clang/LLVM is used for compilation, some symbol names are missing in C level backtrace information. An example:
```
-- C level backtrace information -------------------------------------------
(...snip...)
/var/tmp/ruby.debug/lib/libruby.so.3.1(vm_call_method_each_type+0x6a) [0x7f73856ac33f] ../vm_insnhelper.c:3438
/var/tmp/ruby.debug/lib/libruby.so.3.1(0x7f73856ac29a) [0x7f73856ac29a]
/var/tmp/ruby.debug/lib/libruby.so.3.1(0x7f73856aadf6) [0x7f73856aadf6]
/var/tmp/ruby.debug/lib/libruby.so.3.1(vm_exec_core+0xff7) [0x7f738569c3cd] ../insns.def:792
/var/tmp/ruby.debug/lib/libruby.so.3.1(rb_vm_exec+0x5c9) [0x7f73856a78d4]
/var/tmp/ruby.debug/lib/libruby.so.3.1(rb_ec_exec_node+0xe5) [0x7f73855a1bec] ../eval.c:320
/var/tmp/ruby.debug/lib/libruby.so.3.1(ruby_run_node+0x5a) [0x7f73855a1acf] ../eval.c:379
/var/tmp/ruby.debug/bin/ruby(main+0x73) [0x55c15877ac4b] ../main.c:47
```

This seems to happen because `dladdr(3)` sometimes fills `NULL` in `dli_sname` which is then overwritten to `lines[i].sname` regardless of its previous value.

A patch is attached to fix this issue. It modifies `addr2line.c` so that it does not use `dli_sname` (and also `dli_fname`) when the value is `NULL`.

I also attach another patch that makes `addr2line.c` print source filename even when source lineno is not available (which is the case for `rb_vm_exec` in the above example).

When these two patches are applied, C level backtrace information is printed as follows.
```
-- C level backtrace information -------------------------------------------
(...snip...)
/var/tmp/ruby.debug/lib/libruby.so.3.1(vm_call_method_each_type+0x6a) [0x7fb08928231f] ../vm_insnhelper.c:3438
/var/tmp/ruby.debug/lib/libruby.so.3.1(vm_call_method+0xf6) [0x7fb08928227a] ../vm_insnhelper.c:0
/var/tmp/ruby.debug/lib/libruby.so.3.1(vm_sendish+0x334) [0x7fb089280dd6] ../vm_insnhelper.c:0
/var/tmp/ruby.debug/lib/libruby.so.3.1(vm_exec_core+0xff7) [0x7fb0892723ad] ../insns.def:792
/var/tmp/ruby.debug/lib/libruby.so.3.1(rb_vm_exec+0x5c9) [0x7fb08927d8b4] ../vm.c:0
/var/tmp/ruby.debug/lib/libruby.so.3.1(rb_ec_exec_node+0xe5) [0x7fb089177bcc] ../eval.c:320
/var/tmp/ruby.debug/lib/libruby.so.3.1(ruby_run_node+0x5a) [0x7fb089177aaf] ../eval.c:379
/var/tmp/ruby.debug/bin/ruby(main+0x73) [0x557ed1e0bc4b] ../main.c:47
```

---Files--------------------------------
ruby-addr2line-do-not-overwrite-sname-with-null.patch (1.07 KB)
ruby-addr2line-print-filename-without-lineno.patch (574 Bytes)


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