Crystal: Cannot print traceback if current directory is changed

[lugia-kun]

Under Linux, it fails to raise and exception and call stack will not be printed when following conditions are met:

1. Build a binary executable (crystal run or crystal eval is not applicable)
2. Launch it with relative path.
3. It changes the current directory.
4. It raises an unhandled exception.

Simple reproducible code is:

Dir.cd("/")
raise ""

[momonga@elma ~/crystal x86_64]$ cat foo.cr
Dir.cd(%[/]); raise %[]
[momonga@elma ~/crystal x86_64]$ bin/crystal build foo.cr
Using compiled compiler at `.build/crystal'
[momonga@elma ~/crystal x86_64]$ ./foo
Failed to raise an exception: END_OF_STACK
[0x446df6] *CallStack::print_backtrace:Int32 +118
[0x42d4b6] __crystal_raise +86
[0x42d9de] ???
[0x45be96] *Crystal::System::File::open<String, String, File::Permissions>:Int32 +214
[0x4598d3] *File::new<String, String, File::Permissions, Nil, Nil>:File +67
[0x43df1d] *CallStack::read_dwarf_sections:(Array(Tuple(UInt64, UInt64, String)) | Nil) +109
[0x43dcad] *CallStack::decode_line_number<UInt64>:Tuple(String, Int32, Int32) +45
[0x43d468] *CallStack#decode_backtrace:Array(String) +296
[0x43d322] *CallStack#printable_backtrace:Array(String) +50
[0x481d8d] *Exception+ +77
[0x481bf8] *Exception+ +120
[0x48037a] *AtExitHandlers::run<Int32>:Int32 +490
[0x48936b] *Crystal::main<Int32, Pointer(Pointer(UInt8))>:Int32 +139
[0x437b76] main +6
[0x7fb87b0d4c47] __libc_start_main +231
[0x42c4aa] _start +42
[0x0] ???

Also, using PATH variable to launch the executable, same problem occurs:

1. Build a binary executable
2. Launch it using PATH variable
3. The built executable is not located in the current directory.
4. It raises an unhandled exception.

momonga@elma ~/crystal x86_64]$ bin/crystal build foo.cr
Using compiled compiler at `.build/crystal'
[momonga@elma ~/crystal x86_64]$ (PATH=$(pwd):$PATH; cd ..; foo)
Failed to raise an exception: END_OF_STACK
[0x446df6] *CallStack::print_backtrace:Int32 +118
[0x42d4b6] __crystal_raise +86
[0x42d9de] ???
[0x45be96] *Crystal::System::File::open<String, String, File::Permissions>:Int32 +214
[0x4598d3] *File::new<String, String, File::Permissions, Nil, Nil>:File +67
[0x43df1d] *CallStack::read_dwarf_sections:(Array(Tuple(UInt64, UInt64, String)) | Nil) +109
[0x43dcad] *CallStack::decode_line_number<UInt64>:Tuple(String, Int32, Int32) +45
[0x43d468] *CallStack#decode_backtrace:Array(String) +296
[0x43d322] *CallStack#printable_backtrace:Array(String) +50
[0x481d8d] *Exception+ +77
[0x481bf8] *Exception+ +120
[0x48037a] *AtExitHandlers::run<Int32>:Int32 +490
[0x48936b] *Crystal::main<Int32, Pointer(Pointer(UInt8))>:Int32 +139
[0x437b76] main +6
[0x7fbd5463bc47] __libc_start_main +231
[0x42c4aa] _start +42
[0x0] ???

Output of crystal version is:

Using compiled compiler at `.build/crystal'
Crystal 0.31.0-dev [6ec323f1d] (2019-08-13)

LLVM: 8.0.1
Default target: x86_64-unknown-linux-gnu

This can be shell-dependent: I'm using Bash 5.0.7.

[asterite]

Probably related to #7198

[vlazar]

On MacOS it doesn't change dir but shows this:

$ ./test
Unhandled exception:  (Exception)
  from test.cr:2:1 in '__crystal_main'
  from /usr/local/Cellar/crystal/0.31.1/src/crystal/main.cr:97:5 in 'main_user_code'
  from /usr/local/Cellar/crystal/0.31.1/src/crystal/main.cr:86:7 in 'main'
  from /usr/local/Cellar/crystal/0.31.1/src/crystal/main.cr:106:3 in 'main'

Crystal 0.31.1 on MacOS

$ crystal --version
Crystal 0.31.1 (2019-10-02)

LLVM: 8.0.1
Default target: x86_64-apple-macosx

[lugia-kun]

@vlazar It is the expected result for the example. If it fails to change the directory, you should get a proper message, such as "No such file or directory", instead of an empty message.

[rdp]

Possibly fixed https://github.com/crystal-lang/crystal/pull/8807

[bcardiff]

Seems to be fixed on master.