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| author | Ben Gamari <ben@smart-cactus.org> | 2016-04-27 09:57:41 +0200 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2016-04-28 10:13:37 +0200 |
| commit | 5adf8f3b74a4ee11d594b9993493bed4e3521ce2 (patch) | |
| tree | 2a83cc0acf0a40600909abf6b40b79f98c6662f4 | |
| parent | a48ebcc42ad0b9ef69a295495c4f631fe9d55922 (diff) | |
| download | haskell-5adf8f3b74a4ee11d594b9993493bed4e3521ce2.tar.gz | |
Document -fmax-pmcheck-iterations a bit better
| -rw-r--r-- | docs/users_guide/8.0.1-notes.rst | 2 | ||||
| -rw-r--r-- | docs/users_guide/using-warnings.rst | 12 | ||||
| -rw-r--r-- | utils/mkUserGuidePart/Options/Warnings.hs | 5 |
3 files changed, 18 insertions, 1 deletions
diff --git a/docs/users_guide/8.0.1-notes.rst b/docs/users_guide/8.0.1-notes.rst index 51a9602b48..4db68d24f0 100644 --- a/docs/users_guide/8.0.1-notes.rst +++ b/docs/users_guide/8.0.1-notes.rst @@ -352,7 +352,7 @@ Compiler the pattern match checker iterates. Since coverage checking is exponential in the general case, setting a default number of iterations prevents memory and performance blowups. By default, the number of iterations is set to - 10000000 but it can be set to ``n`` with: ``-fmax-pmcheck-iterations=n``. + 2000000 but it can be set with: ``-fmax-pmcheck-iterations=<n>``. If the set number of iterations is exceeded, an informative warning is issued. diff --git a/docs/users_guide/using-warnings.rst b/docs/users_guide/using-warnings.rst index 72e7748dbe..46b6984ed8 100644 --- a/docs/users_guide/using-warnings.rst +++ b/docs/users_guide/using-warnings.rst @@ -516,6 +516,18 @@ of ``-W(no-)*``. h = \[] -> 2 Just k = f y +.. ghc-flag:: -fmax-pmcheck-iterations=<N> + + :default: 2000000 + + Sets how many iterations of the pattern-match checker will perform before + giving up. This limit is to catch cases where pattern-match checking might + be excessively costly (due to the exponential complexity of coverage + checking in the general case). It typically shouldn't be necessary to set + this unless GHC informs you that it has exceeded the pattern match checker's + iteration limit (in which case you may want to consider refactoring your + pattern match, for the sake of future readers of your code. + .. ghc-flag:: -Wincomplete-record-updates .. index:: diff --git a/utils/mkUserGuidePart/Options/Warnings.hs b/utils/mkUserGuidePart/Options/Warnings.hs index 3552172762..31513d92a4 100644 --- a/utils/mkUserGuidePart/Options/Warnings.hs +++ b/utils/mkUserGuidePart/Options/Warnings.hs @@ -117,6 +117,11 @@ warningsOptions = , flagType = DynamicFlag , flagReverse = "-Wno-incomplete-uni-patterns" } + , flag { flagName = "-Wmax-pmcheck-iterations=<N>" + , flagDescription = + "the iteration limit for the pattern match checker" + , flagType = DynamicFlag + } , flag { flagName = "-Wincomplete-record-updates" , flagDescription = "warn when a record update could fail" , flagType = DynamicFlag |