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LLDB crash when hitting up arrow in expression evaluator #49189

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rupprecht opened this issue Apr 5, 2021 · 3 comments
Closed

LLDB crash when hitting up arrow in expression evaluator #49189

rupprecht opened this issue Apr 5, 2021 · 3 comments
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bugzilla Issues migrated from bugzilla lldb

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@rupprecht
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Bugzilla Link 49845
Resolution FIXED
Resolved on Apr 15, 2021 12:26
Version unspecified
OS Linux
CC @JDevlieghere
Fixed by commit(s) f49a444

Extended Description

This is at trunk. When you are prompted to enter expressions:

$ lldb
(lldb) e
Enter expressions, then terminate with an empty line to evaluate:
1:

... and then you hit the up arrow, it crashes (usually*):

$ lldb
(lldb) e
Enter expressions, then terminate with an empty line to evaluate:
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0. Program arguments: lldb
#​0 0x00000000003b337a llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /home/rupprecht/src/llvm-project/llvm/lib/Support/Unix/Signals.inc:565:11
#​1 0x00000000003b354b PrintStackTraceSignalHandler(void*) /home/rupprecht/src/llvm-project/llvm/lib/Support/Unix/Signals.inc:632:1
#​2 0x00000000003b1b5b llvm::sys::RunSignalHandlers() /home/rupprecht/src/llvm-project/llvm/lib/Support/Signals.cpp:70:5
#​3 0x00000000003b3ca1 SignalHandler(int) /home/rupprecht/src/llvm-project/llvm/lib/Support/Unix/Signals.inc:407:1
#​4 0x00007fba26d9d140 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14140)
#​5 0x00007fba178fd6f0 std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::length() const (/usr/lib/x86_64-linux-gnu/libstdc++.so.6+0x1496f0)
#​6 0x00007fba1e3dc9ff lldb_private::Editline::CountRowsForLine(std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> > const&) /home/rupprecht/src/llvm-project/lldb/source/Host/common/Editline.cpp:434:53
#​7 0x00007fba1e3dc90c lldb_private::Editline::GetLineIndexForLocation(lldb_private::line_editor::CursorLocation, int) /home/rupprecht/src/llvm-project/lldb/source/Host/common/Editline.cpp:370:12
#​8 0x00007fba1e3dcab7 lldb_private::Editline::MoveCursor(lldb_private::line_editor::CursorLocation, lldb_private::line_editor::CursorLocation) /home/rupprecht/src/llvm-project/lldb/source/Host/common/Editline.cpp:392:7
#​9 0x00007fba1e3dd3ac lldb_private::Editline::RecallHistory(lldb_private::line_editor::HistoryOperation) /home/rupprecht/src/llvm-project/lldb/source/Host/common/Editline.cpp:528:3
#​10 0x00007fba1e3de5fe lldb_private::Editline::PreviousLineCommand(int) /home/rupprecht/src/llvm-project/lldb/source/Host/common/Editline.cpp:779:5
#​11 0x00007fba1e3e2237 lldb_private::Editline::ConfigureEditor(bool)::$_7::operator()(editline*, int) const /home/rupprecht/src/llvm-project/lldb/source/Host/common/Editline.cpp:1162:13
#​12 0x00007fba1e3e21fb lldb_private::Editline::ConfigureEditor(bool)::$_7::__invoke(editline*, int) /home/rupprecht/src/llvm-project/lldb/source/Host/common/Editline.cpp:1161:41
#​13 0x00007fba16e47fc4 el_wgets (/usr/lib/x86_64-linux-gnu/libedit.so.2+0x10fc4)
#​14 0x00007fba1e3e1a78 lldb_private::Editline::GetLines(int, lldb_private::StringList&, bool&) /home/rupprecht/src/llvm-project/lldb/source/Host/common/Editline.cpp:1514:3
#​15 0x00007fba1e2e05a9 lldb_private::IOHandlerEditline::GetLines(lldb_private::StringList&, bool&) /home/rupprecht/src/llvm-project/lldb/source/Core/IOHandler.cpp:520:5
#​16 0x00007fba1e2e07dd lldb_private::IOHandlerEditline::Run() /home/rupprecht/src/llvm-project/lldb/source/Core/IOHandler.cpp:562:11
#​17 0x00007fba1e2a071d lldb_private::Debugger::RunIOHandlers() /home/rupprecht/src/llvm-project/lldb/source/Core/Debugger.cpp:868:16
#​18 0x00007fba1e424985 lldb_private::CommandInterpreter::RunCommandInterpreter(lldb_private::CommandInterpreterRunOptions&) /home/rupprecht/src/llvm-project/lldb/source/Interpreter/CommandInterpreter.cpp:3089:9
#​19 0x00007fba1dbf629d lldb::SBDebugger::RunCommandInterpreter(bool, bool) /home/rupprecht/src/llvm-project/lldb/source/API/SBDebugger.cpp:1214:42
#​20 0x0000000000295ada Driver::MainLoop() /home/rupprecht/src/llvm-project/lldb/tools/driver/Driver.cpp:677:3
#​21 0x0000000000296d1e main /home/rupprecht/src/llvm-project/lldb/tools/driver/Driver.cpp:940:17

(note the "1:" prompt line got eaten)

  • The first time I tried to run it, it didn't crash, but it gave me bogus history results. I guess it happened to venture into junk memory without triggering a segfault.
@JDevlieghere
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I can reproduce this by adding an empty line to the lldb-expr-widehistory:

_HiStOrY_V2_
foo\012

bar\012

The issue appears to be that Editline::RecallHistory assumes that m_current_line_index is not empty:

    m_current_line_index = (int)m_input_lines.size() - 1;

We can either return an error when that happens:

  if (new_input_lines.empty())
    return CC_ERROR;

Or we can modify SplitLines to return a vector with an empty entry when passed the empty string.

std::vector<EditLineStringType> SplitLines(const EditLineStringType &input) {
  std::vector<EditLineStringType> result;
  if (input.empty()) {
    result.emplace_back();
    return result;
  }
  ...

@rupprecht
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The CC_ERROR suggestion seems to cause really funky behavior (and causes crashes in other scenarios), but making SplitLines never return an empty vector seems to work nicely. Patch in http://go/phab/D100048 does this.

I was able to get an empty entry in the history file organically (i.e. without directly twiddling it) by entering the expression evaluator and hitting enter.

@rupprecht
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Forgot to close this. And thanks for suggesting the fix!

@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 11, 2021
This issue was closed.
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@rupprecht @JDevlieghere