C-Valgrind

Step 1 : Install valgrind - Dynamic analyser

$ sudo apt-get install valgrind Reading package lists... Done Building dependency tree Reading state information... Done The following packages were automatically installed and are no longer required: g++-7 gcc-8-base:i386 gir1.2-mutter-2 libargon2-0 libbind9-160 libbison-dev libboost-date-time1.65.1 libboost-filesystem1.65.1 libboost-iostreams1.65.1 libboost-locale1.65.1 libboost-system1.65.1 libboost-thread1.65.1 libcapnp-0.6.1 libcdio17 libclang1-6.0 libcomerr2:i386 libcommons-dbcp-java libcommons-pool-java libcwidget3v5 libdns-export1100 libdns1100 libdouble-conversion1 libecj-java libevent-2.1-6 libffi6:i386 libgdbm5 libgl1-mesa-glx:i386 libgmime-3.0-0 libgnome-desktop-3-17 libgspell-1-1 libgweather-3-15 libhogweed4:i386 libhunspell-1.6-0 libicu60:i386 libip4tc0 libip6tc0 libiptc0 libirs-export160 libirs160 libisc-export169 libisc169 libisccc160 libisccfg-export160 libisccfg160 libisl19 libjs-sphinxdoc libjs-underscore libjson-c3 liblinear3 libllvm10:i386 libllvm11 libllvm11:i386 libllvm6.0 liblouis14 liblouisutdml8 liblwres160 libmagickcore-6.q16-3 libmagickcore-6.q16-3-extra libmagickwand-6.q16-3 libmozjs-52-0 libmutter-2-0 libncurses5:i386 libnettle6:i386 libnss-myhostname libntfs-3g88 liborcus-0.13-0 libperl5.26 libpoppler73 libpotrace0 libprocps6 libprotobuf-lite10 libprotobuf10 libprotoc10 libpython-all-dev libpython3.6 libpython3.6-dev libpython3.6-minimal libpython3.6-stdlib libqgsttools-p1 libqpdf21 libraw16 libreadline7 libruby2.5 libsane1 libsane1:i386 libsndio6.1:i386 libspeexdsp1:i386 libstdc++-7-dev libsynctex1 libtexlua52 libtinfo5:i386 libtomcat8-java libvpx5 libwireshark11 libwiretap8 libwscodecs2 libwsutil9 nplan python-all python-all-dev python-asn1crypto python-bzrlib python-cffi-backend python-configobj python-configparser python-crypto python-cryptography python-entrypoints python-enum34 python-httplib2 python-idna python-ipaddress python-keyring python-launchpadlib python-lazr.restfulclient python-lazr.uri python-oauth python-pycurl python-secretstorage python-simplejson python-wadllib python-wheel python-xdg python-zope.interface python3-asn1crypto python3-oauth python3-zope.interface python3.6 python3.6-dev python3.6-minimal ruby-did-you-mean ruby2.5 shim wireshark-gtk Use 'sudo apt autoremove' to remove them. Suggested packages: valgrind-dbg valgrind-mpi kcachegrind alleyoop valkyrie The following NEW packages will be installed: valgrind 0 upgraded, 1 newly installed, 0 to remove and 26 not upgraded. Need to get 20.3 MB of archives. After this operation, 90.0 MB of additional disk space will be used. Get:1 http://in.archive.ubuntu.com/ubuntu focal-updates/main amd64 valgrind amd64 1:3.15.0-1ubuntu9.1 [20.3 MB] Fetched 20.3 MB in 2s (10.9 MB/s) Selecting previously unselected package valgrind. (Reading database ... 424171 files and directories currently installed.) Preparing to unpack .../valgrind_1%3a3.15.0-1ubuntu9.1_amd64.deb ... Unpacking valgrind (1:3.15.0-1ubuntu9.1) ... Setting up valgrind (1:3.15.0-1ubuntu9.1) ... Processing triggers for man-db (2.9.1-1) ... Processing triggers for doc-base (0.10.9) ... Processing 1 added doc-base file... Registering documents with scrollkeeper...

Step 2 : Create a file test.c with memleak
#include <stdio.h> #include <stdlib.h> int main() { char *p; // Allocation #1 of 30 bytes p = (char *) malloc(30); // Allocation #2 of 12 bytes p = (char *) malloc(8); free(p); // Allocation #3 of 16 bytes p = (char *) malloc(25); return 0; }

Step 3 : Compile test.c
$ gcc -o test -g test.c

Step 4 : Run program with valgrind

$ valgrind --tool=memcheck --leak-check=yes --show-reachable=yes --num-callers=20 --track-fds=yes ./test -s ==66488== Memcheck, a memory error detector ==66488== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al. ==66488== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info ==66488== Command: ./test -s ==66488== ==66488== ==66488== FILE DESCRIPTORS: 3 open at exit. ==66488== Open file descriptor 2: /dev/pts/6 ==66488== <inherited from parent> ==66488== ==66488== Open file descriptor 1: /dev/pts/6 ==66488== <inherited from parent> ==66488== ==66488== Open file descriptor 0: /dev/pts/6 ==66488== <inherited from parent> ==66488== ==66488== ==66488== HEAP SUMMARY: ==66488== in use at exit: 55 bytes in 2 blocks ==66488== total heap usage: 3 allocs, 1 frees, 63 bytes allocated ==66488== ==66488== 25 bytes in 1 blocks are definitely lost in loss record 1 of 2 ==66488== at 0x483B7F3: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so) ==66488== by 0x1091A6: main (in /home/test/Desktop/training/valgrind/test) ==66488== ==66488== 30 bytes in 1 blocks are definitely lost in loss record 2 of 2 ==66488== at 0x483B7F3: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so) ==66488== by 0x10917E: main (in /home/test/Desktop/training/valgrind/test) ==66488== ==66488== LEAK SUMMARY: ==66488== definitely lost: 55 bytes in 2 blocks ==66488== indirectly lost: 0 bytes in 0 blocks ==66488== possibly lost: 0 bytes in 0 blocks ==66488== still reachable: 0 bytes in 0 blocks ==66488== suppressed: 0 bytes in 0 blocks ==66488== ==66488== For lists of detected and suppressed errors, rerun with: -s ==66488== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)

Step 5 : Fix the memleaks in file test.c and compile again
#include <stdio.h> #include <stdlib.h> int main() { char *p; // Allocation #1 of 30 bytes p = (char *) malloc(30); free(p); // Allocation #2 of 12 bytes p = (char *) malloc(8); free(p); // Allocation #3 of 16 bytes p = (char *) malloc(25); free(p); return 0; }

Step 6 : Run program with valgrind

$ valgrind --tool=memcheck --leak-check=yes --show-reachable=yes --num-callers=20 --track-fds=yes ./test -s ==66595== Memcheck, a memory error detector ==66595== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al. ==66595== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info ==66595== Command: ./test -s ==66595== ==66595== ==66595== FILE DESCRIPTORS: 3 open at exit. ==66595== Open file descriptor 2: /dev/pts/6 ==66595== <inherited from parent> ==66595== ==66595== Open file descriptor 1: /dev/pts/6 ==66595== <inherited from parent> ==66595== ==66595== Open file descriptor 0: /dev/pts/6 ==66595== <inherited from parent> ==66595== ==66595== ==66595== HEAP SUMMARY: ==66595== in use at exit: 0 bytes in 0 blocks ==66595== total heap usage: 3 allocs, 3 frees, 63 bytes allocated ==66595== ==66595== All heap blocks were freed -- no leaks are possible ==66595== ==66595== For lists of detected and suppressed errors, rerun with: -s ==66595== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)