Installed valgrind on my WSL and I was a bit confused.
Problem: I get a lot of allocated bytes even though my program doesn't do anything.
main.cpp:
#include <iostream>
using namespace std;
int main() {
cout << "I'm testing valgrind!" << endl;
return 0;
}
The result of calling valgrind:
==435== Memcheck, a memory error detector
==435== Copyright (C) 2002-2017, and GNU GPLd, by Julian Seward et al.
==435== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==435== Command: ./start
==435==
==435== error calling PR_SET_PTRACER, vgdb might block
I'm testing valgrind!
==435==
==435== HEAP SUMMARY:
==435== in use at exit: 0 bytes in 0 blocks
==435== total heap usage: 2 allocs, 2 frees, 73,728 bytes allocated
==435==
==435== All heap blocks were freed -- no leaks are possible
==435==
==435== For lists of detected and suppressed errors, rerun with: -s
==435== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
I actually have two questions:
Why do I get so many allocated bytes?
How do I get rid of this? (In my univercity server valgrind doesn't show these bytes so I was wondering if I could do that too..)
If you are curious and want to see what these allocations are, run with
--run-libc-freeres=no --run-cxx-freeres=no -s --leak-check=full --show-reachable=yes
As said in the comments, don't worry about this. All that matters are the errors.
Related
I was developing a C++ program and everything was working fine. Then, while I was programming, I ran make and ran my program like usual. But during the execution of it all, my computer crashed and shut itself off. I reopened my computer and ran make again but this time it gave me a bunch of errors.
Everything seemed off, like my whole computer is corrupted. But everything was working as intended in my operating system except the stuff related to my program. I've tried making a new c++ project, it works just fine. I've tried deleting the project and re-compiling it from github to no avail.
I managed to compile the program in the end but now it gives me a seg fault. The first thing my program does is to print out Starting... to the screen, but this segfault occurs without ever printing that, so it led me to believe that this error is linker related. (Even when the make command was failing, before I fixed it, it told me there was a linker error)
Here is what valgrind says:
turgut#turgut-N56VZ:~/Desktop/CppProjects/videoo-render$ valgrind bin/Renderer
==7521== Memcheck, a memory error detector
==7521== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==7521== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==7521== Command: bin/Renderer
==7521==
==7521== Invalid read of size 1
==7521== at 0x484FBD4: strcmp (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==7521== by 0x121377: __static_initialization_and_destruction_0 (OpenGLRenderer.cpp:111)
==7521== by 0x121377: _GLOBAL__sub_I__ZN6OpenGL7Texture5max_zE (OpenGLRenderer.cpp:197)
==7521== by 0x659FEBA: call_init (libc-start.c:145)
==7521== by 0x659FEBA: __libc_start_main##GLIBC_2.34 (libc-start.c:379)
==7521== by 0x1216A4: (below main) (in /home/turgut/Desktop/CppProjects/videoo-render/bin/Renderer)
==7521== Address 0x0 is not stack'd, malloc'd or (recently) free'd
==7521==
==7521==
==7521== Process terminating with default action of signal 11 (SIGSEGV)
==7521== Access not within mapped region at address 0x0
==7521== at 0x484FBD4: strcmp (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==7521== by 0x121377: __static_initialization_and_destruction_0 (OpenGLRenderer.cpp:111)
==7521== by 0x121377: _GLOBAL__sub_I__ZN6OpenGL7Texture5max_zE (OpenGLRenderer.cpp:197)
==7521== by 0x659FEBA: call_init (libc-start.c:145)
==7521== by 0x659FEBA: __libc_start_main##GLIBC_2.34 (libc-start.c:379)
==7521== by 0x1216A4: (below main) (in /home/turgut/Desktop/CppProjects/videoo-render/bin/Renderer)
==7521== If you believe this happened as a result of a stack
==7521== overflow in your program's main thread (unlikely but
==7521== possible), you can try to increase the size of the
==7521== main thread stack using the --main-stacksize= flag.
==7521== The main thread stack size used in this run was 8388608.
==7521==
==7521== HEAP SUMMARY:
==7521== in use at exit: 72,741 bytes in 3 blocks
==7521== total heap usage: 3 allocs, 0 frees, 72,741 bytes allocated
==7521==
==7521== LEAK SUMMARY:
==7521== definitely lost: 0 bytes in 0 blocks
==7521== indirectly lost: 0 bytes in 0 blocks
==7521== possibly lost: 0 bytes in 0 blocks
==7521== still reachable: 72,741 bytes in 3 blocks
==7521== suppressed: 0 bytes in 0 blocks
==7521== Rerun with --leak-check=full to see details of leaked memory
==7521==
==7521== For lists of detected and suppressed errors, rerun with: -s
==7521== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
Segmentation fault (core dumped)
turgut#turgut-N56VZ:~/Desktop/Cpp
OpenGLRenderer.cpp:197 is just the end of the file and here is what's writeen in OpenGLRenderer.cpp:111:
static bool __debug = strcmp(getenv("DEBUG"), "true") == 0;
It says that there is an error with strcmp but I've tried using that function on a different project and it worked just fine.
What could be the reason for this? I'm on ubuntu 22.04, gcc verison 11.2.0.
this segfault occurs without ever printing that, so it led me to believe that this error is linker related.
The linker is not involved in your program running, so it can't be "linker related".
There is a dynamic loader (if your program uses shared libraries), so perhaps that's what you meant.
In any case, the crash is happening because OpenGLRenderer.cpp:111 (probably in libGL.so) is calling strcmp() with one of the arguments being NULL (which is not a valid thing to do). This does happen before main.
This line:
static bool __debug = strcmp(getenv("DEBUG"), "true") == 0;
is buggy: it will crash when DEBUG is not set in the environment (getenv("DEBUG") will return NULL in that case).
As a workaround, you can run export DEBUG=off, before running your program and the crash will go away.
It's unclear whether you inserted this line into OpenGLRenderer.cpp yourself or whether it was already present, but it's buggy either way.
P.S. A correct way to initialize __debug could be:
static const char *debug_str = getenv("DEBUG");
static const bool debug = strcmp(debug_str == NULL ? "off" : debug_str, "true") == 0;
P.P.S. Avoid using identifiers prefixed with __ (such as __debug) -- they are reserved.
Issue:
I have a weird issue that I wasn't expecting. I have a class called Answers
and within the header is this:
class Answer
{
char* aText;
bool b_correct;
public:
Answer():aText(0){;} //default constructor
}
The main (testing) driver code is this:
int main(void)
{
static const unsigned int MAX_ANSWERS = 5;
Answer answers[MAX_ANSWERS];
}
The (unexpected) weirdness I am getting is that there is an alloc happening, and I haven't used a new anywhere in my code yet. I'm guessing that the char* is calling this in the initialization list.
I am using valgrind to test my code, and I'm getting 11 allocs and 10 frees. When I remove the initializer of :aText(0), the extra alloc goes away.
I get that this is badly constructed code. I am following a course outline to learn how to write in C++. Can someone please help me understand how the memory is allocated or what's happening during the initialization list to cause a call to new?
I know the error is coming from the code shown. I know the extra alloc is happening When I compile and run just this code.
Valgrind Output:
==12598== Memcheck, a memory error detector
==12598== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==12598== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==12598== Command: ./Answers
==12598==
==12598==
==12598== HEAP SUMMARY:
==12598== in use at exit: 72,704 bytes in 1 blocks
==12598== total heap usage: 1 allocs, 0 frees, 72,704 bytes allocated
==12598==
==12598== LEAK SUMMARY:
==12598== definitely lost: 0 bytes in 0 blocks
==12598== indirectly lost: 0 bytes in 0 blocks
==12598== possibly lost: 0 bytes in 0 blocks
==12598== still reachable: 72,704 bytes in 1 blocks
==12598== suppressed: 0 bytes in 0 blocks
==12598== Rerun with --leak-check=full to see details of leaked memory
==12598==
==12598== For counts of detected and suppressed errors, rerun with: -v
==12598== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
Platform Information:
Fedora 22
gcc.x86_64 5.1.1-4.fc22
valgrind.x86_64 1:3.10.1-13.fc22
codeblocks.x86_64 13.12-14.fc22
This is a known GCC 5.1 bug, not a valgrind bug.
Details here:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64535
Possible workarounds:
Downgrade GCC to an earlier version or wait for Valgrind to update a fix for this error. Both solutions are being worked on by their respective communities.
I'm writing a program that uses PCL kinfu and I'm using openCV face detection. I had some heap problems so I isolated the openCV's code to try and check if the problem is over there. After commenting out almost everything, I came across something strange. There is only a global declaration of the 'CascadeClassifier' class, and it causes valgrind to alert on possibly lost and still reachable blocks. Commenting out this declaration works fine. I'm really not sure what's going on and would appreciate any help.
I'm attaching my problematic code (without the commented out parts).
Thanks!
#include "opencv2/objdetect/objdetect.hpp"
using namespace cv;
CascadeClassifier c;
int main() {
return 0;
}
**Valgrind output:**
==3316== Memcheck, a memory error detector
==3316== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==3316== Using Valgrind-3.10.0.SVN and LibVEX; rerun with -h for copyright info
==3316== Command: ./test
==3316==
==3316==
==3316== HEAP SUMMARY:
==3316== in use at exit: 297,370 bytes in 1,393 blocks
==3316== total heap usage: 3,446 allocs, 2,053 frees, 655,130 bytes allocated
==3316==
==3316== LEAK SUMMARY:
==3316== definitely lost: 0 bytes in 0 blocks
==3316== indirectly lost: 0 bytes in 0 blocks
==3316== possibly lost: 4,676 bytes in 83 blocks
==3316== still reachable: 292,694 bytes in 1,310 blocks
==3316== suppressed: 0 bytes in 0 blocks
==3316== Rerun with --leak-check=full to see details of leaked memory
==3316==
==3316== For counts of detected and suppressed errors, rerun with: -v
==3316== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
For me there're two possible explanations:
If you trust Valgrind - might be some leak in opencv code and therefore somebody should investigate it more in details from opencv devs (why don't you create an appropriate ticket with that issue?)
or
There is not any leak cause you clearly have 'possibly' word there. And then you shouln't care much. What kind of heap issue did you have on the beginning before you commented out some code?
BTW using classes that are not POD (Plain Old Data) in the global scope (static memory) is not recommended. Do you have the same problem when you move CascadeClassifier object to the local scope (main())?
try again like this:
#include "opencv2/objdetect/objdetect.hpp"
using namespace cv;
void testmem() {
CascadeClassifier c;
}
int main() {
for (int i=0; i<10; i++)
testmem();
return 0;
}
I'm using valgrind to try and track down a memory leak is the mysql c++ client distributed from mysql.
In both the examples (resultset.cpp) and my own program, there is a single 56 byte block that is not freed. In my own program, I've traced the leak to a call to the mysql client.
Here are the results when I run the test:
valgrind --leak-check=full --show-reachable=yes ./my-executable
==29858== Memcheck, a memory error detector
==29858== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.
==29858== Using Valgrind-3.6.0.SVN-Debian and LibVEX; rerun with -h for copyright info
==29858== Command: ./my-executable
==29858==
==29858==
==29858== HEAP SUMMARY:
==29858== in use at exit: 56 bytes in 1 blocks
==29858== total heap usage: 693 allocs, 692 frees, 308,667 bytes allocated
==29858==
==29858== 56 bytes in 1 blocks are still reachable in loss record 1 of 1
==29858== at 0x4C284A8: malloc (vg_replace_malloc.c:236)
==29858== by 0x400D334: _dl_map_object_deps (dl-deps.c:506)
==29858== by 0x4013652: dl_open_worker (dl-open.c:291)
==29858== by 0x400E9C5: _dl_catch_error (dl-error.c:178)
==29858== by 0x4012FF9: _dl_open (dl-open.c:583)
==29858== by 0x7077BCF: do_dlopen (dl-libc.c:86)
==29858== by 0x400E9C5: _dl_catch_error (dl-error.c:178)
==29858== by 0x7077D26: __libc_dlopen_mode (dl-libc.c:47)
==29858== by 0x72E5FEB: pthread_cancel_init (unwind-forcedunwind.c:53)
==29858== by 0x72E614B: _Unwind_ForcedUnwind (unwind-forcedunwind.c:126)
==29858== by 0x72E408F: __pthread_unwind (unwind.c:130)
==29858== by 0x72DDEB4: pthread_exit (pthreadP.h:265)
==29858==
==29858== LEAK SUMMARY:
==29858== definitely lost: 0 bytes in 0 blocks
==29858== indirectly lost: 0 bytes in 0 blocks
==29858== possibly lost: 0 bytes in 0 blocks
==29858== still reachable: 56 bytes in 1 blocks
==29858== suppressed: 0 bytes in 0 blocks
==29858==
==29858== For counts of detected and suppressed errors, rerun with: -v
==29858== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 8 from 6)
I have a few questions regarding this:
How should I interpret the --show-reachable block?
Is that block useful for me to try and zero in on the error?
If the block is not useful, does valgrind have another mechanism that would help me trace the leak?
If not, is there some other tool (hopefully OSS on linux) to help me narrow this down?
Thanks in advance..
UPDATE: Here is the code that I found on my system for the definition of pthread_exit. I'm not certain that this is the actual source that is being invoked. However, if it is, can anyone explain what might be going wrong?
void
pthread_exit (void *retval)
{
/* specific to PTHREAD_TO_WINTHREAD */
ExitThread ((DWORD) ((size_t) retval)); /* thread becomes signalled so its death can be waited upon */
/*NOTREACHED*/
assert (0); return; /* void fnc; can't return an error code */
}
Reachable just means that the blocks had a valid pointer referencing them in scope when the program exited, which indicates that the program does not explicitly free everything on exit because it relies on the underlying OS to do so. What you should be looking for are lost blocks, where blocks of memory lost all references to them and can no longer be freed.
So, the 56 bytes were probably allocated in main, which did not explicitly free them. What you posted does not show a memory leak. It shows main freeing everything but what main allocated because main assumes that when it dies, all memory will be reclaimed by the kernel.
Specifically, it's pthread (in main) making this assumption (which is a valid assumption on darn near everything found in production written in the last 15+ years). The need to free blocks that still have a valid reference on exit is a bit of a contentious point, but for this specific question all that needs to be mentioned is that the assumption was made.
Edit
It's actually pthread_exit() not cleaning something up on exit, but as explained it probably doesn't need to (or quite possibly can't) once it reaches that point.
Valgrind reports a memory leak when assigning a value to a string.
I used the following simple code to test an memory leak reported by Valgrind.
/******************************************
* FILE: t3.c
* Compiled using : g++ -g t3.c -o t3
*
* $ g++ -v
* Reading specs from /usr/lib/gcc/i686-pc-linux-gnu/3.4.6/specs
* Configured with: ./configure --prefix=/usr --infodir=/share/info --mandir=/share/man
* --enable-languages=c,c++ --with-system-zlib --program-suffix=-3.4 --enable-threads=posix
* Thread model: posix
* gcc version 3.4.6
******************************************/
#include <iostream>
#include <string>
using namespace std;
/**************************************************************
**************************************************************/
int main(int argc, char *argv[])
{
string test = "XXXXXXXXX";
cout << "this is a test " << test << endl;
exit(0);
}
I compile using this command:
$ g++ -g t3.c -o t3
And when I run Valgrind it reports a memory leak when I try to assign a value to a string. I'm using this simple test to investigate some memory leak in the real program, and it seems that using string can cause some sort of problem.
By 0x8048A6F: main (t3.c:23) is the line : string test = "XXXXXXXXX";
Can someone give some hint on such strange behaviour?
[enzo#P0101222 C]$ valgrind --leak-check=full ./t3
==3910== Memcheck, a memory error detector.
==3910== Copyright (C) 2002-2007, and GNU GPL'd, by Julian Seward et al.
==3910== Using LibVEX rev 1732, a library for dynamic binary translation.
==3910== Copyright (C) 2004-2007, and GNU GPL'd, by OpenWorks LLP.
==3910== Using valgrind-3.2.3, a dynamic binary instrumentation framework.
==3910== Copyright (C) 2000-2007, and GNU GPL'd, by Julian Seward et al.
==3910== For more details, rerun with: -v
==3910==
this is a test XXXXXXXXX
==3910==
==3910== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 25 from 1)
==3910== malloc/free: in use at exit: 102 bytes in 3 blocks.
==3910== malloc/free: 4 allocs, 1 frees, 126 bytes allocated.
==3910== For counts of detected errors, rerun with: -v
==3910== searching for pointers to 3 not-freed blocks.
==3910== checked 194,136 bytes.
==3910==
==3910== 16 bytes in 1 blocks are definitely lost in loss record 1 of 3
==3910== at 0x4017846: malloc (m_replacemalloc/vg_replace_malloc.c:149)
==3910== by 0x4018E05: realloc (m_replacemalloc/vg_replace_malloc.c:306)
==3910== by 0x41B441A: argz_append (in /lib/libc-2.2.5.so)
==3910== by 0x41593B9: __newlocale (in /lib/libc-2.2.5.so)
==3910== by 0x40E010B: std::locale::facet::_S_create_c_locale(__locale_struct*&, char const*, __locale_struct*) (c++locale.cc:99)
==3910== by 0x407EF6F: std::locale::facet::_S_initialize_once() (../../.././libstdc++-v3/src/locale.cc:172)
==3910== by 0x407EFB4: std::locale::facet::_S_get_c_locale() (../../.././libstdc++-v3/src/locale.cc:185)
==3910== by 0x407A422: std::ctype<char>::ctype(unsigned short const*, bool, unsigned) (/usr3/BUILD/gcc/gcc-3.4.6/i686-pc-linux-gnu/libstdc++-v3/include/i686-pc-linux-gnu/bits/ctype_noninline.h:104)
==3910== by 0x40801D5: std::locale::_Impl::_Impl(unsigned) (/usr3/BUILD/gcc/gcc-3.4.6/libstdc++-v3/libsupc++/new:92)
==3910== by 0x4080EED: std::locale::_S_initialize_once() (/usr3/BUILD/gcc/gcc-3.4.6/libstdc++-v3/libsupc++/new:92)
==3910== by 0x4080F84: std::locale::_S_initialize() (../../.././libstdc++-v3/src/locale_init.cc:155)
==3910== by 0x4080FE7: std::locale::locale() (../../.././libstdc++-v3/src/locale_init.cc:102)
==3910==
==3910==
==3910== 22 bytes in 1 blocks are possibly lost in loss record 2 of 3
==3910== at 0x4017C38: operator new(unsigned) (m_replacemalloc/vg_replace_malloc.c:163)
==3910== by 0x40BF2C4: std::string::_Rep::_S_create(unsigned, unsigned, std::allocator<char> const&) (/usr3/BUILD/gcc/gcc-3.4.6/i686-pc-linux-gnu/libstdc++-v3/include/ext/new_allocator.h:81)
==3910== by 0x40C1CE4: char* std::string::_S_construct<char const*>(char const*, char const*, std::allocator<char> const&, std::forward_iterator_tag) (/usr3/BUILD/gcc/gcc-3.4.6/i686-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.tcc:150)
==3910== by 0x40C1E15: std::string::string(char const*, std::allocator<char> const&) (/usr3/BUILD/gcc/gcc-3.4.6/i686-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:1386)
==3910== **by 0x8048A6F: main (t3.c:23)**
==3910==
==3910== LEAK SUMMARY:
==3910== definitely lost: 16 bytes in 1 blocks.
==3910== **possibly lost: 22 bytes in 1 blocks.**
==3910== still reachable: 64 bytes in 1 blocks.
==3910== suppressed: 0 bytes in 0 blocks.
==3910== Reachable blocks (those to which a pointer was found) are not shown.
==3910== To see them, rerun with: --leak-check=full --show-reachable=yes
[enzo#P0101222 C]$
Because you call exit(0), so the string destructor is never invoked. Just use return 0.
To elaborate, the constructor of std::string allocates heap memory to store the string, relying on the destructor to deallocate that memory. If you declare a string object on the stack, the destructor will automatically be invoked when the string object goes out of scope, thus freeing the memory. But exit is really a C mechanism; it immediately exits the program without performing stack-unwinding meaning that C++ destructors for local stack objects will not be called.
If you allocate five strings, do you get five times the memory leak, or is it still the same amount? If it's the same amount, then you probably don't have a leak at all. Some libraries allocate memory for internal bookkeeping/efficiency/et cetera that doesn't get released until after valgrind stops looking. These get picked up as memory leaks because your program caused the allocation but never caused a deallocation. If it's five times the amount, then your implementation of string may be at fault. I agree with Charles Salvia though... try again with return 0; instead of exit(0); and see if that changes anything.
Despite having no exit(0) at the end of program I had similar problem with false positives with std::string . I was statically linking with libstdc++. Switching linking option to shared and compiling with GLIBCXX_FORCE_NEW suppressed the warnings.
In one of my computer science classes we were told that Valgrind outputs information about strings that we shouldn't worry about. Here's the suppression file that they gave us for strings:
https://gist.github.com/garfieldnate/eb7ba0011b57a9c63e7c3dcafb689e15