Stack traces not displaying correctly on macOS

[Paul Rockwell]

I've found that stack traces don't display correctly with GNU APL on macOS platforms (Intel and Apple Silicon). Examining the source for Backtrace.cc, I've found that function Backtrace::show_item() is expecting the string passed to it to look like this:

  // ./apl(_ZN10APL_parser9nextTokenEv+0x1dc) [0x80778dc]

  // │││││                             │││││   │││││││││

  // └┴┴┴┴─── program name             │││││   └┴┴┴┴┴┴┴┴───── abs_addr

  //                                   └┴┴┴┴───────────────── asm_offset

The macOS system function backtrace_symbols() - called by Backtrace::show() returns the strings in this format:

  //

  // 14  apl                                 0x00000001000a93f0 _ZN9Workspace19immediate_executionEb + 68

  // ││  └┴┴─── program name                 ││││││││││││││││││ ││││││││││││││││││||||||||||||||||||   └┴─── asm_offset

  // └┴─── stack level                       ││││││││││││││││││ └┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴─── function name

  //                                         └┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴───── abs_addr

  //

These strings don't match what the code is looking for, so the stack trace doesn't contain any useful information.

I prototyped some changes to Backtrace::show_item() to be able to recognize that GNU APL is being built on Apple macOS, and parse the macOS backtrace_symbols() string format. The resulting code seems to compile and work correctly on Intel Linux and macOS (both on Intel and Apple Silicon CPUs).

I've attached the diffs between SVN 1745 and my changed code. (I also made some other changes to the code to reflect use of nullptr and '\0' instead of the number 0 to improve the contextual clarity of some of the code. There are also a couple of changes to remove some compiler warnings on macOS for unreachable code)

You're welcome to use them if you find them useful.

- Paul Rockwell

Backtrace.cc.diffs.zip
Description: Zip archive