1. 27 Jan, 2016 1 commit
  2. 13 Jan, 2016 1 commit
  3. 08 Jan, 2016 1 commit
    • Simon Marlow's avatar
      Enable stack traces with ghci -fexternal-interpreter -prof · 6be09e88
      Simon Marlow authored
      Summary:
      The main goal here is enable stack traces in GHCi.  After this change,
      if you start GHCi like this:
      
        ghci -fexternal-interpreter -prof
      
      (which requires packages to be built for profiling, but not GHC
      itself) then the interpreter manages cost-centre stacks during
      execution and can produce a stack trace on request.  Call locations
      are available for all interpreted code, and any compiled code that was
      built with the `-fprof-auto` familiy of flags.
      
      There are a couple of ways to get a stack trace:
      
      * `error`/`undefined` automatically get one attached
      * `Debug.Trace.traceStack` can be used anywhere, and prints the current
        stack
      
      Because the interpreter is running in a separate process, only the
      interpreted code is running in profiled mode and the compiler itself
      isn't slowed down by profiling.
      
      The GHCi debugger still doesn't work with -fexternal-interpreter,
      although this patch gets it a step closer.  Most of the functionality
      of breakpoints is implemented, but the runtime value introspection is
      still not supported.
      
      Along the way I also did some refactoring and added type arguments to
      the various remote pointer types in `GHCi.RemotePtr`, so there's
      better type safety and documentation in the bridge code between GHC
      and ghc-iserv.
      
      Test Plan: validate
      
      Reviewers: bgamari, ezyang, austin, hvr, goldfire, erikd
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1747
      
      GHC Trac Issues: #11047, #11100
      6be09e88
  4. 21 Dec, 2015 1 commit
    • Simon Marlow's avatar
      Maintain cost-centre stacks in the interpreter · c8c44fd9
      Simon Marlow authored
      Summary:
      Breakpoints become SCCs, so we have detailed call-stack info for
      interpreted code.  Currently this only works when GHC is compiled with
      -prof, but D1562 (Remote GHCi) removes this constraint so that in the
      future call stacks will be available without building your own GHCi.
      
      How can you get a stack trace?
      
      * programmatically: GHC.Stack.currentCallStack
      * I've added an experimental :where command that shows the stack when
        stopped at a breakpoint
      * `error` attaches a call stack automatically, although since calls to
        `error` are often lifted out to the top level, this is less useful
        than it might be (ImplicitParams still works though).
      * Later we might attach call stacks to all exceptions
      
      Other related changes in this diff:
      
      * I reduced the number of places that get ticks attached for
        breakpoints.  In particular there was a breakpoint around the whole
        declaration, which was often redundant because it bound no variables.
        This reduces clutter in the stack traces and speeds up compilation.
      
      * I tidied up some RealSrcSpan stuff in InteractiveUI, and made a few
        other small cleanups
      
      Test Plan: validate
      
      Reviewers: ezyang, bgamari, austin, hvr
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1595
      
      GHC Trac Issues: #11047
      c8c44fd9
  5. 18 Dec, 2015 1 commit
  6. 17 Dec, 2015 1 commit
    • Simon Marlow's avatar
      Remote GHCi, -fexternal-interpreter · 4905b83a
      Simon Marlow authored
      Summary:
      (Apologies for the size of this patch, I couldn't make a smaller one
      that was validate-clean and also made sense independently)
      
      (Some of this code is derived from GHCJS.)
      
      This commit adds support for running interpreted code (for GHCi and
      TemplateHaskell) in a separate process.  The functionality is
      experimental, so for now it is off by default and enabled by the flag
      -fexternal-interpreter.
      
      Reaosns we want this:
      
      * compiling Template Haskell code with -prof does not require
        building the code without -prof first
      
      * when GHC itself is profiled, it can interpret unprofiled code, and
        the same applies to dynamic linking.  We would no longer need to
        force -dynamic-too with TemplateHaskell, and we can load ordinary
        objects into a dynamically-linked GHCi (and vice versa).
      
      * An unprofiled GHCi can load and run profiled code, which means it
        can use the stack-trace functionality provided by profiling without
        taking the performance hit on the compiler that profiling would
        entail.
      
      Amongst other things; see
      https://ghc.haskell.org/trac/ghc/wiki/RemoteGHCi for more details.
      
      Notes on the implementation are in Note [Remote GHCi] in the new
      module compiler/ghci/GHCi.hs.  It probably needs more documenting,
      feel free to suggest things I could elaborate on.
      
      Things that are not currently implemented for -fexternal-interpreter:
      
      * The GHCi debugger
      * :set prog, :set args in GHCi
      * `recover` in Template Haskell
      * Redirecting stdin/stdout for the external process
      
      These are all doable, I just wanted to get to a working validate-clean
      patch first.
      
      I also haven't done any benchmarking yet.  I expect there to be slight hit
      to link times for byte code and some penalty due to having to
      serialize/deserialize TH syntax, but I don't expect it to be a serious
      problem.  There's also lots of low-hanging fruit in the byte code
      generator/linker that we could exploit to speed things up.
      
      Test Plan:
      * validate
      * I've run parts of the test suite with
      EXTRA_HC_OPTS=-fexternal-interpreter, notably tests/ghci and tests/th.
      There are a few failures due to the things not currently implemented
      (see above).
      
      Reviewers: simonpj, goldfire, ezyang, austin, alanz, hvr, niteria, bgamari, gibiansky, luite
      
      Subscribers: thomie
      
      Differential Revision: https://phabricator.haskell.org/D1562
      4905b83a