[ASDAlexander77]

Summary

On Windows, WinDbg and Visual Studio can't debug --emit=jit: the JIT registers its code only through the GDB JIT interface, and its objects carry CodeView, which nothing reads from there. --emit=jit --jit-native links the JIT cache's objects into one DLL with a PDB in __jit and loads it with the system loader instead of RTDyld. The debugger then sees an ordinary module with symbols and source lines.

• linkBinary (link.h, exe.cpp): the link line buildExe built, now taking its objects, output, "shared" and extra arguments as parameters, so it can be called mid-run. buildExe keeps InitLLVM and the command-line globals and calls it. A quiet link shows the linker's output only if the link fails.

• jitnative.cpp: the link, plus a small generated object of host functions:

  • init sends assert/abort reports to stderr (no modal dialogs) and flushes on SIGABRT;
  • flush is called after the program and before TerminateProcess, because the DLL's static C runtime owns the program's stdout buffer.

  The DLL and PDB are reused while the objects and options are the same. Earlier ones, and stale temporary files from killed links, are removed.

• The static default library is linked into the DLL. Through the default library DLL's import library, a program that reads the library's data doesn't link: Map reads PrimeHelpers.hashCollisionThreshold by its plain name, and only an __imp_ reference resolves a DLL data export. AOT --emit=dll has the same failure today, which will be fixed separately.

• jit.cpp: one runner for both loaders. In this mode neither the default library's DLL nor TypeScriptRuntime.dll is loaded.

• --jit-native implies --di unless --opt is given. It is an error without the JIT cache, and is ignored with a warning off Windows.

Design and as-built notes: tslang/docs/jit-native-dll-debugging-design.md.

Testing

• New test-jit-native-dll (test/tester/jit-native.cmake, Windows): a two-module program runs, its DLL and PDB are reused on the next run and relinked after the module changes, and exit code, uncaught exception, failing assert and the no-cache error are checked. Where cdb is installed, a breakpoint in the imported module is hit at its source line. With the flush disabled the test fails (output lost).
• ctest -C Release -R "test-jit-|test-compile-": 4463/4463 passed (Windows, release build).
• By hand: rc and gc (gc with --opt, and with --di against a debug runtime library), with the default library, cdb breakpoints by function and by source line.
• Not built on Linux: there the option only warns.

🤖 Generated with Claude Code