[lldb] Interactive command line interface nonfunctional on Windows with cross-platform libedit

[lulle2007200]

I have built LLDB 19.1.6 on windows with libedit support using this cross-platform libedit port: https://github.com/michaeljclark/libedit.

Here is the cmake command used:

cmake -S llvm -B build -G Ninja `
-DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_INSTALL_PREFIX="install" `
-DCMAKE_CXX_COMPILER=cl -DCMAKE_C_COMPILER=cl `
-DLLDB_EMBED_PYTHON_HOME=0 `
-DLLVM_ENABLE_PROJECTS="lldb;clang" `
-DLLDB_INCLUDE_TESTS=Off `
-DLLDB_ENABLE_LIBEDIT=On `
-DLLDB_ENABLE_CURSES=Off `
-DLLDB_ENABLE_LZMA=Off `
-DLLDB_ENABLE_LIBXML2=Off `
-DLLDB_ENABLE_PYTHON=Off `
-DLLDB_ENABLE_LUA=Off `
-DLibEdit_LIBRARIES="C:\Program Files (x86)\Windows Kits\10\Lib\10.0.22621.0\um\x64\Crypt32.Lib;C:\Program Files (x86)\Windows Kits\10\Lib\10.0.22621.0\um\x64\Winmm.Lib;C:\Program Files (x86)\Windows Kits\10\Lib\10.0.22621.0\um\x64\UserEnv.Lib;C:\Program Files (x86)\Windows Kits\10\Lib\10.0.22621.0\um\x64\Secur32.Lib;C:\Users\Christoph\Dev\libedit\install\lib\edit.lib;C:\libedit\install\lib\compat.lib;C:\libedit\install\lib\regex.lib;C:\libedit\install\lib\terminfo.lib;C:\libedit\install\lib\edit.lib;C:\libedit\install\lib\pdcurses.lib" `
-DLibEdit_INCLUDE_DIRS="C:\libedit\libedit"

The getline function libedit provides in libedit\compat\win32 is incomplete and doesn't return -1 on errors or when no characters were read and doesn't handle memory allocations. I have replaced it with the following:

ssize_t getline(char **lineptr, size_t *n, FILE *stream)
{
   size_t lim = *n;
   size_t size = *n;
   char *s = *lineptr;

   if(s && !lim){
      abort();
   }

   if(!s){
      size = 0;
      lim = 0;
   }

   int c, i = 0;
   while (--lim > 0 && (c=fgetc(stream)) != EOF && c != '\n'){
      if(i >= size){
         size += 80;
         char *ptr = (char*)realloc(s, size);
         if(!ptr){
            goto error;
         }
         s = ptr;
      }
      s[i++] = c;
   }

   if (c == '\n'){
      if(i >= size){
         size += 80;
         char *ptr = (char*)realloc(s, size);
         if(!ptr){
            goto error;
         }
         s = ptr;
      }
      s[i++] = c;
   }

   if(i >= size){
      size += 80;
      char *ptr = (char*)realloc(s, size);
      if(!ptr){
         goto error;
      }
      s = ptr;
   }
   s[i] = '\0';

   *lineptr = s;
   *n = size;

   if(i){
      return i;
   }
   return -1;

   error:
   free(s);
   *lineptr = NULL;
   *n = 0;
   return -1;
}

Pretty ugly, but works.

The resulting lldb executable is not functional.
Launching and attaching to a process by pid (e.g. lldb --attach-pid xxxx) etc. works fine, but the interactive command line is non-functional and does not accept any user keyboard input (command line stays blank).

Here is a call stack when suspending lldb:

SelectHelper.cpp Line 228   C++                   liblldb.dll!SelectHelper::Select()                                                                                                                                                                                                
ConnectionFileDescriptorPosix.cpp Line 477  C++   liblldb.dll!lldb_private::ConnectionFileDescriptor::BytesAvailable(const lldb_private::Timeout<std::ratio<1,1000000>> & timeout, lldb_private::Status * error_ptr)                                                                
ConnectionFileDescriptorPosix.cpp Line 272  C++   liblldb.dll!lldb_private::ConnectionFileDescriptor::Read(void * dst, unsigned __int64 dst_len, const lldb_private::Timeout<std::ratio<1,1000000>> & timeout, lldb::ConnectionStatus & status, lldb_private::Status * error_ptr)   
Editline.cpp Line 576   C++                       liblldb.dll!lldb_private::Editline::GetCharacter(wchar_t * c)                                                                                                                                                                     
read.c Line 401 C                                 liblldb.dll!el_wgetc(editline * el, wchar_t * cp)                                                                                                                                                                                 
read.c Line 225 C                                 liblldb.dll!read_getcmd(editline * el, unsigned char * cmdnum, wchar_t * ch)                                                                                                                                                  
read.c Line 514 C                                 liblldb.dll!el_wgets(editline * el, int * nread)                                                                                                                                                                              
eln.c Line 72   C                                 liblldb.dll!el_gets(editline * el, int * nread)                                                                                                                                                                               
Editline.cpp Line 1497  C++                       liblldb.dll!lldb_private::Editline::GetLine(std::string & line, bool & interrupted)                                                                                                                                           
IOHandler.cpp Line 354  C++                       liblldb.dll!lldb_private::IOHandlerEditline::GetLine(std::string & line, bool & interrupted)                                                                                                                                  
IOHandler.cpp Line 596  C++                       liblldb.dll!lldb_private::IOHandlerEditline::Run()                                                                                                                                                                                
Debugger.cpp Line 1107  C++                       liblldb.dll!lldb_private::Debugger::RunIOHandlers()                                                                                                                                                                           
CommandInterpreter.cpp Line 3404    C++           liblldb.dll!lldb_private::CommandInterpreter::RunCommandInterpreter(lldb_private::CommandInterpreterRunOptions & options)                                                                                                         
Line 1253 C++                                     liblldb.dll!lldb::SBDebugger::RunCommandInterpreter(bool auto_handle_events, bool spawn_thread) SBDebugger.cpp                                                                                                                  
Driver.cpp Line 621 C++                           lldb.exe!Driver::MainLoop()                                                                                                                                                                                                   
Driver.cpp Line 807 C++                           lldb.exe!main(int argc, const char * * argv)                                                                                                                                                                                  
	

In particular, the call

const int num_set_fds = ::select(nfds, read_fdset_ptr, write_fdset_ptr, error_fdset_ptr, tv_ptr);

in SelectHelper.cpp line 214 always fails and the loop

while (handle == m_io_sp->GetWaitableHandle()) { ... }`

in ConnectionFileDescriptorPosix.cpp line 473 is never left.

I'm not too familiar with the inner workings of lldb.

[llvmbot]

@llvm/issue-subscribers-lldb

Author: None (lulle2007200)

I have built LLDB 19.1.6 on windows with libedit support using this cross-platform libedit port: [https://github.com/michaeljclark/libedit](https://github.com/michaeljclark/libedit).

Here is the cmake command used:

cmake -S llvm -B build -G Ninja `
-DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_INSTALL_PREFIX="install" `
-DCMAKE_CXX_COMPILER=cl -DCMAKE_C_COMPILER=cl `
-DLLDB_EMBED_PYTHON_HOME=0 `
-DLLVM_ENABLE_PROJECTS="lldb;clang" `
-DLLDB_INCLUDE_TESTS=Off `
-DLLDB_ENABLE_LIBEDIT=On `
-DLLDB_ENABLE_CURSES=Off `
-DLLDB_ENABLE_LZMA=Off `
-DLLDB_ENABLE_LIBXML2=Off `
-DLLDB_ENABLE_PYTHON=Off `
-DLLDB_ENABLE_LUA=Off `
-DLibEdit_LIBRARIES="C:\Program Files (x86)\Windows Kits\10\Lib\10.0.22621.0\um\x64\Crypt32.Lib;C:\Program Files (x86)\Windows Kits\10\Lib\10.0.22621.0\um\x64\Winmm.Lib;C:\Program Files (x86)\Windows Kits\10\Lib\10.0.22621.0\um\x64\UserEnv.Lib;C:\Program Files (x86)\Windows Kits\10\Lib\10.0.22621.0\um\x64\Secur32.Lib;C:\Users\Christoph\Dev\libedit\install\lib\edit.lib;C:\libedit\install\lib\compat.lib;C:\libedit\install\lib\regex.lib;C:\libedit\install\lib\terminfo.lib;C:\libedit\install\lib\edit.lib;C:\libedit\install\lib\pdcurses.lib" `
-DLibEdit_INCLUDE_DIRS="C:\libedit\libedit"

The getline function libedit provides in libedit\compat\win32 is incomplete and doesn't return -1 on errors or when no characters were read and doesn't handle memory allocations. I have replaced it with the following:

ssize_t getline(char **lineptr, size_t *n, FILE *stream)
{
   size_t lim = *n;
   size_t size = *n;
   char *s = *lineptr;

   if(s && !lim){
      abort();
   }

   if(!s){
      size = 0;
      lim = 0;
   }

   int c, i = 0;
   while (--lim > 0 && (c=fgetc(stream)) != EOF && c != '\n'){
      if(i >= size){
         size += 80;
         char *ptr = (char*)realloc(s, size);
         if(!ptr){
            goto error;
         }
         s = ptr;
      }
      s[i++] = c;
   }

   if (c == '\n'){
      if(i >= size){
         size += 80;
         char *ptr = (char*)realloc(s, size);
         if(!ptr){
            goto error;
         }
         s = ptr;
      }
      s[i++] = c;
   }

   if(i >= size){
      size += 80;
      char *ptr = (char*)realloc(s, size);
      if(!ptr){
         goto error;
      }
      s = ptr;
   }
   s[i] = '\0';

   *lineptr = s;
   *n = size;

   if(i){
      return i;
   }
   return -1;

   error:
   free(s);
   *lineptr = NULL;
   *n = 0;
   return -1;
}

Pretty ugly, but works.

The resulting lldb executable is not functional.
Launching and attaching to a process by pid (e.g. lldb --attach-pid xxxx) etc. works fine, but the interactive command line is non-functional and does not accept any user keyboard input (command line stays blank).

Here is a call stack when suspending lldb:

SelectHelper.cpp Line 228   C++                   liblldb.dll!SelectHelper::Select()                                                                                                                                                                                                
ConnectionFileDescriptorPosix.cpp Line 477  C++   liblldb.dll!lldb_private::ConnectionFileDescriptor::BytesAvailable(const lldb_private::Timeout<std::ratio<1,1000000>> & timeout, lldb_private::Status * error_ptr)                                                                
ConnectionFileDescriptorPosix.cpp Line 272  C++   liblldb.dll!lldb_private::ConnectionFileDescriptor::Read(void * dst, unsigned __int64 dst_len, const lldb_private::Timeout<std::ratio<1,1000000>> & timeout, lldb::ConnectionStatus & status, lldb_private::Status * error_ptr)   
Editline.cpp Line 576   C++                       liblldb.dll!lldb_private::Editline::GetCharacter(wchar_t * c)                                                                                                                                                                     
read.c Line 401 C                                 liblldb.dll!el_wgetc(editline * el, wchar_t * cp)                                                                                                                                                                                 
read.c Line 225 C                                 liblldb.dll!read_getcmd(editline * el, unsigned char * cmdnum, wchar_t * ch)                                                                                                                                                  
read.c Line 514 C                                 liblldb.dll!el_wgets(editline * el, int * nread)                                                                                                                                                                              
eln.c Line 72   C                                 liblldb.dll!el_gets(editline * el, int * nread)                                                                                                                                                                               
Editline.cpp Line 1497  C++                       liblldb.dll!lldb_private::Editline::GetLine(std::string & line, bool & interrupted)                                                                                                                                           
IOHandler.cpp Line 354  C++                       liblldb.dll!lldb_private::IOHandlerEditline::GetLine(std::string & line, bool & interrupted)                                                                                                                                  
IOHandler.cpp Line 596  C++                       liblldb.dll!lldb_private::IOHandlerEditline::Run()                                                                                                                                                                                
Debugger.cpp Line 1107  C++                       liblldb.dll!lldb_private::Debugger::RunIOHandlers()                                                                                                                                                                           
CommandInterpreter.cpp Line 3404    C++           liblldb.dll!lldb_private::CommandInterpreter::RunCommandInterpreter(lldb_private::CommandInterpreterRunOptions & options)                                                                                                         
Line 1253 C++                                     liblldb.dll!lldb::SBDebugger::RunCommandInterpreter(bool auto_handle_events, bool spawn_thread) SBDebugger.cpp                                                                                                                  
Driver.cpp Line 621 C++                           lldb.exe!Driver::MainLoop()                                                                                                                                                                                                   
Driver.cpp Line 807 C++                           lldb.exe!main(int argc, const char * * argv)                                                                                                                                                                                  
	

In particular, the call

const int num_set_fds = ::select(nfds, read_fdset_ptr, write_fdset_ptr, error_fdset_ptr, tv_ptr);

in SelectHelper.cpp line 214 always fails and the loop

while (handle == m_io_sp->GetWaitableHandle()) { ... }`

in ConnectionFileDescriptorPosix.cpp line 473 is never left.

I'm not too familiar with the inner workings of lldb.