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| author | Roland Senn <rsx@bluewin.ch> | 2019-10-03 16:37:52 +0200 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2019-10-26 05:20:14 -0400 |
| commit | 1be9c35c940e9a1edbb44a0e7dd51b48529ffb9b (patch) | |
| tree | b8599dbfc9e5fb57193cd3d46a10908d7543d18d /docs | |
| parent | 8916e64e5437c99b82d5610286430328af1d86bc (diff) | |
| download | haskell-1be9c35c940e9a1edbb44a0e7dd51b48529ffb9b.tar.gz | |
Fix #14690 - :steplocal panics after break-on-error
`:steplocal` enables only breakpoints in the current top-level binding.
When a normal breakpoint is hit, then the module name and the break id from the `BRK_FUN` byte code
allow us to access the corresponding entry in a ModBreak table. From this entry we then get the SrcSpan
(see compiler/main/InteractiveEval.hs:bindLocalsAtBreakpoint).
With this source-span we can then determine the current top-level binding, needed for the steplocal command.
However, if we break at an exception or at an error, we don't have an BRK_FUN byte-code, so we don't have any source information.
The function `bindLocalsAtBreakpoint` creates an `UnhelpfulSpan`, which doesn't allow us to determine the current top-level binding.
To avoid a `panic`, we have to check for `UnhelpfulSpan` in the function `ghc/GHCi/UI.hs:stepLocalCmd`.
Hence a :steplocal command after a break-on-exception or a break-on-error is not possible.
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/users_guide/ghci.rst | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/docs/users_guide/ghci.rst b/docs/users_guide/ghci.rst index 72e2d66e12..d1229ed0d5 100644 --- a/docs/users_guide/ghci.rst +++ b/docs/users_guide/ghci.rst @@ -2884,7 +2884,10 @@ commonly used commands. .. ghci-cmd:: :steplocal Enable only breakpoints in the current top-level binding and resume - evaluation at the last breakpoint. + evaluation at the last breakpoint. Continuation with + :ghci-cmd:`:steplocal` is not possible if this last breakpoint was + hit by an error (:ghc-flag:`-fbreak-on-error`) or an + exception (:ghc-flag:`-fbreak-on-exception`). .. ghci-cmd:: :stepmodule |