#9395: Debug.Trace should not use %s for format string -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 7.8.2 libraries/base | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: Incorrect | Related Tickets: result at runtime | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by ezyang): OK, it's a little trickier than just specifying a new format string; I forgot that {{{ #include "stdio.h" int main() { printf("%.*s", 4, "AA\0B"); return 0; } }}} only outputs AA, even with the length description. So we can't use debugBelch. This raises the question, why are we using debugBelch at all? Some archaeology later: {{{ [project @ 2005-01-28 23:33:57 by krasimir] - The output from uncaught exceptions handler is redirected to RTS's errorBelch. - The output from Debug.Trace is redirected to RTS's debugBelch - Usually errorBelch and debugBelch messages go to stderr except for Windows GUI applications. For GUI applications the Debug.Trace output is redirected to debug console and the exceptions message is displayed in message box. }}} It also seems like a good idea generally to bypass Haskell-lands buffering. Unfortunately, printf style output is a hard-coded assumption for `RtsMsgFunction`, so we can't easily swap it out without introducing another function for raw output. Maybe, alternately, Debug.Trace should munge out null bytes? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9395#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#9395: Debug.Trace should not use %s for format string -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: bug | Status: merge Priority: normal | Milestone: Component: | Version: 7.8.2 libraries/base | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: Incorrect | Related Tickets: result at runtime | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Changes (by ezyang): * status: new => merge -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9395#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#9395: Debug.Trace should not use %s for format string -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: bug | Status: closed Priority: normal | Milestone: Component: Core Libraries | Version: 7.8.2 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by Austin Seipp ): In [changeset:"a82364c9410d35fa9cb5031d553212267c3628c5/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="a82364c9410d35fa9cb5031d553212267c3628c5" Don't truncate traceEvents to 512 bytes (#8309) Summary: Don't call postLogMsg to post a user msg, because it truncates messages to 512 bytes. Rename traceCap_stderr and trace_stderr to vtraceCap_stderr and trace_stderr, to signal that they take a va_list (similar to vdebugBelch vs debugBelch). See #3874 for the original reason behind traceFormatUserMsg. See the commit msg in #9395 (d360d440) for a discussion about using null-terminated strings vs strings with an explicit length. Test Plan: Run `cabal install ghc-events` and inspect the result of `ghc-events show` on an eventlog file created with `ghc -eventlog Test.hs` and `./Test +RTS -l`, where Test.hs contains: ``` import Debug.Trace main = traceEvent (replicate 510 'a' ++ "bcd") $ return () ``` Depends on D655. Reviewers: austin Reviewed By: austin Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D656 GHC Trac Issues: #8309 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9395#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler