Native FileDialog corrupts memory

Short description: see attached file "filedialog_bug_valgrind_screenshot.png"

Long description follows:
Memory corruption occurs when using FileDialog qml component when native dialog pops up. The corruption was detected with valgrind tool. After invoking FileDialog the stack becomes corrupted and the application is not usable.

valgrind's full output when running attached (example) project:

build-fdialog_bug-Desktop_Qt_5_8_0_GCC_64bit-Debug $ valgrind --leak-check=yes ./fdialog_bug
==26044== Memcheck, a memory error detector
==26044== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==26044== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==26044== Command: ./fdialog_bug
==26044==
QML debugging is enabled. Only use this in a safe environment.
==26044== Conditional jump or move depends on uninitialised value(s)
==26044== at 0xC4A0094: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC446425: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC448C6D: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC55E5EF: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC55FB1D: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC4801E4: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC480561: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC4805F7: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC55DFD4: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC566ED0: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC18B875: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC18BBF7: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044==
==26044== Syscall param write(buf) points to uninitialised byte(s)
==26044== at 0x7B8A76D: ??? (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B1111E: _IO_file_write@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B12898: _IO_do_write@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B1091F: _IO_file_sync@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B05F2E: fflush (in /usr/lib64/libc-2.22.so)
==26044== by 0xC452F3B: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC4547F6: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC451F7B: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC4464CA: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC448C6D: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC55E5EF: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC55FB1D: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== Address 0x1fe55018 is in a rw- anonymous segment
==26044==
==26044== Conditional jump or move depends on uninitialised value(s)
==26044== at 0xC4A0094: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC446425: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC446CDC: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC592170: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC5935B0: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC4801E4: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC480561: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC4805F7: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC592456: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC56AEEA: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC43D0F4: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC41FEAB: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044==
==26058== Warning: invalid file descriptor 1024 in syscall close()
==26058== Warning: invalid file descriptor 1025 in syscall close()
==26058== Warning: invalid file descriptor 1026 in syscall close()
==26058== Warning: invalid file descriptor 1027 in syscall close()
==26058== Use --log-fd=<number> to select an alternative log fd.
==26058== Warning: invalid file descriptor 1028 in syscall close()
==26058== Warning: invalid file descriptor 1029 in syscall close()
==26058== Warning: invalid file descriptor 1030 in syscall close()
==26044== Thread 5 QSGRenderThread:
==26044== Conditional jump or move depends on uninitialised value(s)
==26044== at 0xC451D62: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC451F35: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC232D23: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC24694F: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC21FCE9: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC2BA523: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0x584BE54: QOpenGLShaderProgram::link() (in /opt/Qt/5.8/gcc_64/lib/libQt5Gui.so.5.8.0)
==26044== by 0x4FB18E9: QSGDefaultRenderContext::compileShader(QSGMaterialShader*, QSGMaterial*, char const*, char const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F81529: ??? (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F82728: QSGBatchRenderer::Renderer::renderMergedBatch(QSGBatchRenderer::Batch const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F8320C: QSGBatchRenderer::Renderer::renderBatches() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F88883: QSGBatchRenderer::Renderer::render() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044==
==26044== Conditional jump or move depends on uninitialised value(s)
==26044== at 0xC451C92: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC451F35: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC232D23: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC24694F: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC21FCE9: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC2BA523: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0x584BE54: QOpenGLShaderProgram::link() (in /opt/Qt/5.8/gcc_64/lib/libQt5Gui.so.5.8.0)
==26044== by 0x4FB18E9: QSGDefaultRenderContext::compileShader(QSGMaterialShader*, QSGMaterial*, char const*, char const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F81529: ??? (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F82728: QSGBatchRenderer::Renderer::renderMergedBatch(QSGBatchRenderer::Batch const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F8320C: QSGBatchRenderer::Renderer::renderBatches() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F88883: QSGBatchRenderer::Renderer::render() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044==
==26044== Conditional jump or move depends on uninitialised value(s)
==26044== at 0xC451CA9: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC451F35: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC232D23: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC24694F: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC21FCE9: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC2BA523: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0x584BE54: QOpenGLShaderProgram::link() (in /opt/Qt/5.8/gcc_64/lib/libQt5Gui.so.5.8.0)
==26044== by 0x4FB18E9: QSGDefaultRenderContext::compileShader(QSGMaterialShader*, QSGMaterial*, char const*, char const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F81529: ??? (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F82728: QSGBatchRenderer::Renderer::renderMergedBatch(QSGBatchRenderer::Batch const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F8320C: QSGBatchRenderer::Renderer::renderBatches() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F88883: QSGBatchRenderer::Renderer::render() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044==
==26044== Conditional jump or move depends on uninitialised value(s)
==26044== at 0xC451CED: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC451F35: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC232D23: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC24694F: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC21FCE9: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC2BA523: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0x584BE54: QOpenGLShaderProgram::link() (in /opt/Qt/5.8/gcc_64/lib/libQt5Gui.so.5.8.0)
==26044== by 0x4FB18E9: QSGDefaultRenderContext::compileShader(QSGMaterialShader*, QSGMaterial*, char const*, char const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F81529: ??? (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F82728: QSGBatchRenderer::Renderer::renderMergedBatch(QSGBatchRenderer::Batch const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F8320C: QSGBatchRenderer::Renderer::renderBatches() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F88883: QSGBatchRenderer::Renderer::render() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044==
==26044== Conditional jump or move depends on uninitialised value(s)
==26044== at 0xC451D82: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC451F35: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC232D23: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC24694F: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC21FCE9: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC2BA523: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0x584BE54: QOpenGLShaderProgram::link() (in /opt/Qt/5.8/gcc_64/lib/libQt5Gui.so.5.8.0)
==26044== by 0x4FB18E9: QSGDefaultRenderContext::compileShader(QSGMaterialShader*, QSGMaterial*, char const*, char const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F81529: ??? (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F82728: QSGBatchRenderer::Renderer::renderMergedBatch(QSGBatchRenderer::Batch const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F8320C: QSGBatchRenderer::Renderer::renderBatches() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F88883: QSGBatchRenderer::Renderer::render() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044==
==26044== Conditional jump or move depends on uninitialised value(s)
==26044== at 0xC451D23: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC451F35: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC232D23: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC24694F: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC21FCE9: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC2BA523: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0x584BE54: QOpenGLShaderProgram::link() (in /opt/Qt/5.8/gcc_64/lib/libQt5Gui.so.5.8.0)
==26044== by 0x4FB18E9: QSGDefaultRenderContext::compileShader(QSGMaterialShader*, QSGMaterial*, char const*, char const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F81529: ??? (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F82728: QSGBatchRenderer::Renderer::renderMergedBatch(QSGBatchRenderer::Batch const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F8320C: QSGBatchRenderer::Renderer::renderBatches() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F88883: QSGBatchRenderer::Renderer::render() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044==
==26044== Conditional jump or move depends on uninitialised value(s)
==26044== at 0xC451D88: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC451F35: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC232D23: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC24694F: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC21FCE9: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC2BA523: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0x584BE54: QOpenGLShaderProgram::link() (in /opt/Qt/5.8/gcc_64/lib/libQt5Gui.so.5.8.0)
==26044== by 0x4FB18E9: QSGDefaultRenderContext::compileShader(QSGMaterialShader*, QSGMaterial*, char const*, char const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F81529: ??? (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F82728: QSGBatchRenderer::Renderer::renderMergedBatch(QSGBatchRenderer::Batch const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F8320C: QSGBatchRenderer::Renderer::renderBatches() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044== by 0x4F88883: QSGBatchRenderer::Renderer::render() (in /opt/Qt/5.8/gcc_64/lib/libQt5Quick.so.5.8.0)
==26044==
==26044== Syscall param write(buf) points to uninitialised byte(s)
==26044== at 0x7B8A76D: ??? (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B1111E: _IO_file_write@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B12898: _IO_do_write@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B1199C: _IO_file_xsputn@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B06E4A: fwrite (in /usr/lib64/libc-2.22.so)
==26044== by 0xC452F29: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC4547F6: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC451F7B: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC232D23: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC24694F: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC21FCE9: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC2BA523: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== Address 0x1fe55ce9 is in a rw- anonymous segment
==26044==
==26044== Thread 6 QSGRenderThread:
==26044== Syscall param write(buf) points to uninitialised byte(s)
==26044== at 0x7B8A76D: ??? (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B1111E: _IO_file_write@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B12898: _IO_do_write@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B12DAA: _IO_file_overflow@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B13B4F: _IO_default_xsputn (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B117E6: _IO_file_xsputn@@GLIBC_2.2.5 (in /usr/lib64/libc-2.22.so)
==26044== by 0x7B06E4A: fwrite (in /usr/lib64/libc-2.22.so)
==26044== by 0xC452F0C: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC4547F6: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC451F7B: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC4464CA: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== by 0xC448C6D: ??? (in /usr/lib64/nvidia-340xx/libnvidia-glcore.so.340.96)
==26044== Address 0x20044fe6 is in a rw- anonymous segment
==26044==
==26044== Thread 1:
==26044== Syscall param writev(vector[...]) points to uninitialised byte(s)
==26044== at 0x7B902FD: ??? (in /usr/lib64/libc-2.22.so)
==26044== by 0xDF5D538: ??? (in /usr/lib64/libxcb.so.1.1.0)
==26044== by 0xDF5D92C: ??? (in /usr/lib64/libxcb.so.1.1.0)
==26044== by 0xDF5E086: ??? (in /usr/lib64/libxcb.so.1.1.0)
==26044== by 0xDF5E253: xcb_flush (in /usr/lib64/libxcb.so.1.1.0)
==26044== by 0x16C9396F: QXcbWindow::hide() (in /opt/Qt/5.8/gcc_64/lib/libQt5XcbQpa.so.5.8.0)
==26044== by 0x558CF52: QWindow::setVisible(bool) (in /opt/Qt/5.8/gcc_64/lib/libQt5Gui.so.5.8.0)
==26044== by 0x1D64D136: ??? (in /opt/Qt/5.8/gcc_64/qml/QtQuick/Dialogs/libdialogplugin.so)
==26044== by 0x1D64AB9B: ??? (in /opt/Qt/5.8/gcc_64/qml/QtQuick/Dialogs/libdialogplugin.so)
==26044== by 0x1D65A6C8: ??? (in /opt/Qt/5.8/gcc_64/qml/QtQuick/Dialogs/libdialogplugin.so)
==26044== by 0x1D65AAEF: ??? (in /opt/Qt/5.8/gcc_64/qml/QtQuick/Dialogs/libdialogplugin.so)
==26044== by 0x1D658934: ??? (in /opt/Qt/5.8/gcc_64/qml/QtQuick/Dialogs/libdialogplugin.so)
==26044== Address 0xe757129 is 4,537 bytes inside a block of size 21,152 alloc'd
==26044== at 0x4C2A988: calloc (vg_replace_malloc.c:711)
==26044== by 0xDF5CEEB: xcb_connect_to_fd (in /usr/lib64/libxcb.so.1.1.0)
==26044== by 0xDF60C20: xcb_connect_to_display_with_auth_info (in /usr/lib64/libxcb.so.1.1.0)
==26044== by 0xDA42F59: _XConnectXCB (in /usr/lib64/libX11.so.6.3.0)
==26044== by 0xDA33AF1: XOpenDisplay (in /usr/lib64/libX11.so.6.3.0)
==26044== by 0x16C7DC4A: QXcbConnection::QXcbConnection(QXcbNativeInterface*, bool, unsigned int, char const*) (in /opt/Qt/5.8/gcc_64/lib/libQt5XcbQpa.so.5.8.0)
==26044== by 0x16C83504: QXcbIntegration::QXcbIntegration(QStringList const&, int&, char**) (in /opt/Qt/5.8/gcc_64/lib/libQt5XcbQpa.so.5.8.0)
==26044== by 0x16A3E43C: ??? (in /opt/Qt/5.8/gcc_64/plugins/platforms/libqxcb.so)
==26044== by 0x556FBFA: QPlatformIntegrationFactory::create(QString const&, QStringList const&, int&, char**, QString const&) (in /opt/Qt/5.8/gcc_64/lib/libQt5Gui.so.5.8.0)
==26044== by 0x557D435: QGuiApplicationPrivate::createPlatformIntegration() (in /opt/Qt/5.8/gcc_64/lib/libQt5Gui.so.5.8.0)
==26044== by 0x557DEDC: QGuiApplicationPrivate::createEventDispatcher() (in /opt/Qt/5.8/gcc_64/lib/libQt5Gui.so.5.8.0)
==26044== by 0x67ED7D5: QCoreApplicationPrivate::init() (in /opt/Qt/5.8/gcc_64/lib/libQt5Core.so.5.8.0)
==26044==
qml: file:file:///etc/passwd

For this example '/etc/password` file was selected in the user prompt.

The source code of the example is attached. The application does not crash, however the report of valgrind tool is enough as a proof of memory corruption.

P.S.
I am available for testing.