Question

  setText mb $ "Hello World"
  qshow mb () -- Segmentation Failt 
  --print ("Hello world") -- it works

我正在使用qtHaskell，但我发现跟踪示例的唯一问题是qshow分段错误。

也许有人有任何想法我该如何尝试修复它？

谢谢。

补充：完整的程序代码：

module Main where

import Qtc.Classes.Qccs
import Qtc.Classes.Gui
import Qtc.ClassTypes.Gui
import Qtc.Core.Base
import Qtc.Gui.Base
import Qtc.Gui.QApplication
import Qtc.Gui.QWidget
import Qtc.Gui.QPushButton
import Qtc.Gui.QAbstractButton
import Qtc.Gui.QMessageBox

type MyQPushButton = QPushButtonSc (CMyQPushButton)
data CMyQPushButton = CMyQPushButton

myQPushButton :: String -> IO (MyQPushButton)
myQPushButton b = qSubClass $ qPushButton b

main :: IO Int
main = do
  qApplication ()
  hello <- myQPushButton "Hello qtHaskell World"
  resize hello (200::Int, 60::Int)
  mb <- qMessageBox hello 
  connectSlot hello "clicked()" hello "click()" $ on_hello_clicked mb
  qshow hello ()
  qApplicationExec ()

on_hello_clicked :: QMessageBox () -> MyQPushButton -> IO ()
on_hello_clicked mb this
  = do
  tt <- text this ()
  setText mb $ "You have clicked " ++ tt
  qshow mb ()

添加了valgrind日志

> > ncdy@Cndy ~/Haskell $ valgrind ./a
> ==13467== Memcheck, a memory error detector
> ==13467== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
> ==13467== Using Valgrind-3.6.0 and LibVEX; rerun with -h for copyright
> info
> ==13467== Command: ./a
> ==13467== 
> 
> ==13467== Syscall param writev(vector[...]) points to
> uninitialised byte(s)
> ==13467==    at 0x40008D2: ??? (in /lib/ld-2.11.2.so)
> ==13467==  Address 0x6e85d97 is 2,703 bytes inside a block of size 16,384
> alloc'd
> ==13467==    at 0x4027834: calloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
> ==13467==    by 0x69C4BD4: XOpenDisplay (in
> /usr/lib/libX11.so.6.3.0)
> ==13467==    by 0x4C505F53: ???
> ==13467== 
> ==13467== 
> ==13467== Process terminating with default action of signal 11 (SIGSEGV)
> ==13467==  General Protection Fault
> ==13467==    at 0x5957480: ??? (in /usr/lib/qt4/libQtGui.so.4.7.1)
> ==13467==    by 0x5B5FD81: ??? (in /usr/lib/qt4/libQtGui.so.4.7.1)
> ==13467==    by 0x5B6BC19: ??? (in /usr/lib/qt4/libQtGui.so.4.7.1)
> ==13467==    by 0x5B71B3C: ??? (in /usr/lib/qt4/libQtGui.so.4.7.1)
> ==13467==    by 0x5AE757D: QPainter::drawPixmap(QRectF const&,
> QPixmap const&, QRectF const&) (in
> /usr/lib/qt4/libQtGui.so.4.7.1)
> ==13467==    by 0xA71AA68: Oxygen::Helper::renderWindowBackground(QPainter*,
> QRect const&, QWidget const*, QWidget
> const*, QColor const&, int, int) (in
> /usr/lib/liboxygenstyle.so.4.5.0)
> ==13467== Invalid free() / delete / delete[]
> ==13467==    at 0x402868B: free (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
> ==13467==    by 0x52F78DB: ??? (in /lib/libc-2.11.2.so)
> ==13467==    by 0x105FFFF: ???
> ==13467==  Address 0x5133a98 is not stack'd, malloc'd or (recently) free'd
> ==13467== 
> ==13467== 
> ==13467== HEAP SUMMARY:
> ==13467==     in use at exit: 1,968,209 bytes in 27,864 blocks
> ==13467==   total heap usage: 65,595 allocs, 37,732 frees, 6,175,162 bytes
> allocated
> ==13467== 
> ==13467== LEAK SUMMARY:
> ==13467==    definitely lost: 18,054 bytes in 259 blocks
> ==13467==    indirectly lost: 94,591 bytes in 628 blocks
> ==13467==      possibly lost: 489,039 bytes in 5,656 blocks
> ==13467==    still reachable: 1,366,525 bytes in 21,321 blocks
> ==13467==         suppressed: 0 bytes in 0 blocks
> ==13467== Rerun with --leak-check=full to see details of leaked memory
> ==13467== 
> ==13467== For counts of detected and suppressed errors, rerun with: -v
> ==13467== Use --track-origins=yes to see where uninitialised values come
> from
> ==13467== ERROR SUMMARY: 3 errors from 2 contexts (suppressed: 15 from 8)
> Segmentation fault

添加：构建命令

ghc --make -package qt -fglasgow-exts -O2 -o a HCK.hs -i

@Foo Bah 问题在12月18日被问到，我无法确定我的答案，但操作系统是Windows7，告诉我究竟能告诉我这个系统是什么？

@Vlad Lazarenko 我知道，但确实是窗户。

@Foo Bah 使用cygwin，是吗？我需要在哪里使用它？我在这台机器上，我可以再次尝试qtHaskell并检查当前的情况，但我想会有另一个版本。

Answer 1

在您的示例中，有一些可能导致麻烦的地方。我强调可能在这里处理内存问题可能非常依赖于你在哪个库中进行内存管理。

首先，您应该在运行垃圾收集时通知qtHaskell。我会把它放在on_hello_clicked程序的末尾。适当的电话是returnGC。在returnGC函数的末尾添加另一个main来电是个好主意。

其次，您的主要功能是指定一个不存在的整数参数。您应将main指定为main :: IO ()

所以，完整的代码是：

module Main where

import Qtc.Classes.Qccs
import Qtc.Classes.Gui
import Qtc.ClassTypes.Gui
import Qtc.Core.Base
import Qtc.Gui.Base
import Qtc.Gui.QApplication
import Qtc.Gui.QWidget
import Qtc.Gui.QPushButton
import Qtc.Gui.QAbstractButton
import Qtc.Gui.QMessageBox

type MyQPushButton = QPushButtonSc (CMyQPushButton)
data CMyQPushButton = CMyQPushButton

myQPushButton :: String -> IO (MyQPushButton)
myQPushButton b = qSubClass $ qPushButton b

main :: IO ()
main = do
  qApplication ()
  hello <- myQPushButton "Hello qtHaskell World"
  resize hello (200::Int, 60::Int)
  mb <- qMessageBox hello 
  connectSlot hello "clicked()" hello "click()" $ on_hello_clicked mb
  qshow hello ()
  qApplicationExec ()
  returnGC

on_hello_clicked :: QMessageBox () -> MyQPushButton -> IO ()
on_hello_clicked mb this
  = do
  tt <- text this ()
  setText mb $ "You have clicked " ++ tt
  qshow mb ()
  returnGC

这在WindowsXP + Cygwin以及MacOS 10.6

上编译并运行良好

Qshow分段错误

1 个答案: