System exception: "cannot lock mutex" when using Util :: XMLConfiguration/AbstractConfiguration --> createView() -> keys() #4844
Description
Describe the bug
My application encounters a Poco SystemException when accessing the keys of a xml sub-view.
To Reproduce
Mini example "poco_bug.cpp":
#include<Poco/Util/AbstractConfiguration.h>
#include<Poco/Util/XMLConfiguration.h>
#include<iostream>
using namespace Poco::Util;
int main()
{
std::vector<std::string> confKeys;
AbstractConfiguration* cfg = new XMLConfiguration("conf.xml");
Poco::Util::AbstractConfiguration* sysView = cfg->createView("prop3");
try {
sysView->keys(confKeys);
} catch (const Poco::SystemException& e) {
std::cerr << "SystemException: " << e.displayText() << std::endl;
std::cerr << "Code: " << e.code() << std::endl;
}
return 0;
}
The try-catch is only used to receive further information.
Read xml "conf.xml":
<config>
<prop1>value1</prop1>
<prop2>value2</prop2>
<prop3>
<prop4 attr="value3"/>
<prop4 attr="value4"/>
</prop3>
<prop5 id="first">value5</prop5>
<prop5 id="second">value6</prop5>
</config>
Compiled and executed with:
g++ poco_bug.cpp -lPocoFoundation -lPocoXML -lPocoUtil -g
./a.out
Expected behavior
Read keys without throwing system exception.
Logs
Output of the mini example:
SystemException: System exception: cannot lock mutex
Code: 0
Output of valgrind:
# valgrind ./a.out
==4743== Memcheck, a memory error detector
==4743== Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward et al.
==4743== Using Valgrind-3.22.0 and LibVEX; rerun with -h for copyright info
==4743== Command: ./a.out
==4743==
==4743== Invalid read of size 4
==4743== at 0x4DC9FE4: pthread_mutex_lock@@GLIBC_2.2.5 (pthread_mutex_lock.c:80)
==4743== by 0x4A43120: ??? (in /usr/lib/x86_64-linux-gnu/libPocoUtil.so.80)
==4743== by 0x4A4720D: Poco::Util::AbstractConfiguration::keys(std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >&) const (in /usr/lib/x86_64-linux-gnu/libPocoUtil.so.80)
==4743== by 0x10A5A4: main (poco_bug.cpp:12)
==4743== Address 0x51e2bd8 is 488 bytes inside a block of size 552 free'd
==4743== at 0x484A61D: operator delete(void*, unsigned long) (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==4743== by 0x10A840: Poco::RefCountedObject::release() const (RefCountedObject.h:82)
==4743== by 0x10AB16: Poco::AutoPtr<Poco::Util::AbstractConfiguration>::~AutoPtr() (AutoPtr.h:96)
==4743== by 0x10A572: main (poco_bug.cpp:10)
==4743== Block was alloc'd at
==4743== at 0x4846FA3: operator new(unsigned long) (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==4743== by 0x4A4B934: Poco::Util::AbstractConfiguration::createView(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (in /usr/lib/x86_64-linux-gnu/libPocoUtil.so.80)
==4743== by 0x10A54D: main (poco_bug.cpp:10)
==4743==
==4743== Invalid read of size 4
==4743== at 0x4DC992C: __pthread_mutex_lock_full (pthread_mutex_lock.c:198)
==4743== by 0x4A43120: ??? (in /usr/lib/x86_64-linux-gnu/libPocoUtil.so.80)
==4743== by 0x4A4720D: Poco::Util::AbstractConfiguration::keys(std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >&) const (in /usr/lib/x86_64-linux-gnu/libPocoUtil.so.80)
==4743== by 0x10A5A4: main (poco_bug.cpp:12)
==4743== Address 0x51e2bd8 is 488 bytes inside a block of size 552 free'd
==4743== at 0x484A61D: operator delete(void*, unsigned long) (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==4743== by 0x10A840: Poco::RefCountedObject::release() const (RefCountedObject.h:82)
==4743== by 0x10AB16: Poco::AutoPtr<Poco::Util::AbstractConfiguration>::~AutoPtr() (AutoPtr.h:96)
==4743== by 0x10A572: main (poco_bug.cpp:10)
==4743== Block was alloc'd at
==4743== at 0x4846FA3: operator new(unsigned long) (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==4743== by 0x4A4B934: Poco::Util::AbstractConfiguration::createView(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (in /usr/lib/x86_64-linux-gnu/libPocoUtil.so.80)
==4743== by 0x10A54D: main (poco_bug.cpp:10)
==4743==
SystemException: System exception: cannot lock mutex
Code: 0
==4743==
==4743== HEAP SUMMARY:
==4743== in use at exit: 54,904 bytes in 20 blocks
==4743== total heap usage: 158 allocs, 138 frees, 177,095 bytes allocated
==4743==
==4743== LEAK SUMMARY:
==4743== definitely lost: 536 bytes in 1 blocks
==4743== indirectly lost: 54,368 bytes in 19 blocks
==4743== possibly lost: 0 bytes in 0 blocks
==4743== still reachable: 0 bytes in 0 blocks
==4743== suppressed: 0 bytes in 0 blocks
==4743== Rerun with --leak-check=full to see details of leaked memory
==4743==
==4743== For lists of detected and suppressed errors, rerun with: -s
==4743== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)
Please add relevant environment information:
- Docker Image ubuntu:24.04
- apt update; apt install g++ libpoco-dev
- (libpoco-dev: Installed: 1.11.0-4.1build2 ; g++: Installed: 4:13.2.0-7ubuntu1)
With poco version 1.9.4 this was working. I also tried newer versions (e.g. 1.12.0, 1.13.3, 1.14.0) and also encountered this problem.