Greetings Gentlemen (and Ladies),
As part of my small and simple framework for making presentations in
Haskell I have a module which, given some text, makes a .tex file and
then converts it to .svg for loading into a cairo canvas.
It features simple caching (performs md5 on the contents of the .tex
file and uses that as the file name... if an .svg by that name exists,
it'll get loaded rather than regenerated).
Unfortunately, it also segfaults once in a while, probably indicating I
have some kind of race condition ... but I can't figure out why. This is
the only point in my code that I think I'm using any concurrency,
although I'm compiling with ghc --make -threaded. Compiling without
-threaded results in a deadlock.
Ubuntu 8.10, 64-bit, GHC 6.8.2.
Any advice? I'm attaching the module in question (79 lines).
Sincerely,
Rafal Kolanski.
module LatexSVG (updateSVG, updateSVG') where
import System.Process
import Control.Concurrent (forkIO)
import Control.Monad (when)
import System.IO
import System.Directory (doesFileExist)
import System.Exit
workingDir = "tex/"
prefix = unlines $
["\\documentclass{minimal} ",
"\\usepackage{graphicx,latexsym,amsmath,url,color}",
"\\usepackage{amssymb,amsmath,wasysym, pst-node, color}",
"\\usepackage{url}",
"\\usepackage{isabelle,isabellesym}",
"%\\usepackage{mathpartir}",
"\\definecolor{dblue}{rgb}{0,0,0.4}",
"\\definecolor{blue}{rgb}{0,0,0.6}",
"\\definecolor{green}{rgb}{0,0.6,0}",
"\\definecolor{gray}{rgb}{0.7,0.7,0.7}",
"\\definecolor{dblue}{rgb}{0,0,0.6}",
"\\definecolor{darkgray}{rgb}{0.4,0.4,0.4}",
"\\definecolor{red}{rgb}{0.6,0,0}",
"\\begin{document}"]
suffix = "\n\\end{document}"
-- Pass text to md5sum and drop the final " -" when returning
hashMD5 text = do
(inp,out,err,pid) <- runInteractiveProcess "md5sum" [] Nothing Nothing
forkIO $ do
hPutStrLn inp text
hClose inp
exit <- waitForProcess pid
case exit of ExitFailure _ -> error "md5sum fail"
_ -> return ()
md5hash <- hGetContents out
return $ takeWhile (\x -> x /= ' ') md5hash
blindExecWithFail cmd args dir = do
(inp,out,err,pid) <- runInteractiveProcess cmd args (Just dir) Nothing
exit <- waitForProcess pid
case exit of ExitFailure _ -> error $ cmd ++ " " ++ (show args) ++ "fail"
_ -> return ()
generateSVG text filebase = do
-- Create a .tex file
writeFile (workingDir ++ filebase ++ ".tex") text
-- Run pdflatex over it
blindExecWithFail "pdflatex" [filebase] workingDir
-- Run pstoedit on resulting .pdf
blindExecWithFail "pstoedit"
["-page 1","-dt","-psarg","-r9600x9600",
filebase ++ ".pdf", filebase ++ ".sk"]
workingDir
-- Run skconvert on resulting .sk
blindExecWithFail "skconvert"
[filebase ++ ".sk", filebase ++ ".svg"]
workingDir
updateSVG' :: [Char] -> [Char] -> [Char] -> IO [Char]
updateSVG' prefix suffix text = do
-- Hash the tex
let tex = prefix ++ text ++ suffix
md5hash <- hashMD5 tex
-- Filenames are the hash prefixed with hash and ending with extension
let filebase = "hash" ++ md5hash
-- See if an svg file by that name exists
svge <- doesFileExist $ workingDir ++ filebase ++ ".svg"
when (not svge) $! do
putStrLn $ filebase ++ ".svg does not exist, creating"
generateSVG tex filebase
return $ workingDir ++ filebase ++ ".svg"
updateSVG :: [Char] -> IO [Char]
updateSVG = updateSVG' prefix suffix
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