diff --git a/.gitignore b/.gitignore
index cab1d1a..4be6400 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,12 +1,16 @@
-# Build results
+# build results
 bin/
 obj/
+*.log
+*.tmp
 
-# user files
-.old*/
+# IDE files
 .vs/
 .vshistory/
 .editorconfig
 *.user
 *.vcxproj.filters
+
+# other files
+.old*/
 current.config
diff --git a/Makefile b/Makefile
index 3f31069..03b6418 100644
--- a/Makefile
+++ b/Makefile
@@ -1,18 +1,56 @@
-all: build_exec
+######################################
+######       Build tasks       #######
+######################################
 
-#####       Build cbuild/default_tasks      ######
-build_exec: 
-	@cbuild/call_task.sh build_exec
-build_exec_dbg: 
-	@cbuild/call_task.sh build_exec_dbg
+all: build_exec_dbg
 
-#####      Launch cbuild/default_tasks      ######
+# generates different profile info
+build_profile:
+	@cbuild/call_task.sh build_profile 2>&1 | tee make_raw.log
+
+# creates executable using profile info generated by build_profile
+build_exec: build_profile
+	@cbuild/call_task.sh build_exec  2>&1 | tee -a make_raw.log
+
+# creates executable with debug info and no optimizations
+build_exec_dbg:
+	@cbuild/call_task.sh build_exec_dbg 2>&1 | tee make_raw.log
+
+######################################
+######       Launch tasks      #######
+######################################
+
+# executes $EXEC_FILE
 exec: build_exec
-	@cbuild/call_task.sh exec
+	@cbuild/call_task.sh exec 2>&1 | tee -a make_raw.log
 
+# executes $EXEC_FILE
+exec_dbg: build_exec_dbg
+	@cbuild/call_task.sh exec 2>&1 | tee -a make_raw.log
+
+# executes $EXEC_FILE with valgrind memory checker
 valgrind: build_exec_dbg
-	@cbuild/call_task.sh valgrind
+	@cbuild/call_task.sh valgrind 2>&1 | tee -a make_raw.log
 
-#####	    	Recompile kerep.a			######
+######################################
+######       Other tasks       #######
+######################################
+
+# deletes generated files
+clean:
+	@cbuild/call_task.sh clean 2>&1 | tee make_raw.log
+
+# removes all unreadable characters copied from stdio
+fix_log:
+	sed 's/[^[:blank:][:print:]]//g' make_raw.log \
+		| sed 's/\[0;[0-9][0-9]m//g' \
+		| sed 's/\[0;[0-9]m//g' \
+		| sed 's/\[[0-9][0-9]m//g' \
+		| sed 's/\[[0-9]m//g' \
+		| sed 's/  H  //g' \
+		| sed 's/\[3gH  //g' \
+		> make_fixed.log
+
+# recompile kerep.a in the next build task
 rebuild_kerep: 
 	@cbuild/call_task.sh rebuild_kerep
diff --git a/cbuild b/cbuild
index 81358b7..112fcc0 160000
--- a/cbuild
+++ b/cbuild
@@ -1 +1 @@
-Subproject commit 81358b72f8dc602d694f46ea42c2b64d9b0b41c6
+Subproject commit 112fcc04652d6ce65fbde215cd3d1f8935db2a7c
diff --git a/default.config b/default.config
index ed2159b..5603f05 100644
--- a/default.config
+++ b/default.config
@@ -1,6 +1,6 @@
 #!/bin/bash
-CBUILD_VERSION=4
-CONFIG_VERSION=1
+CBUILD_VERSION=5
+CONFIG_VERSION=2
 
 PROJECT=scolte
 CMP_C=gcc
@@ -14,44 +14,85 @@ SRC_CPP="$(  find src -name '*.cpp')"
 #TESTS_C="$(  find tests -name '*.c')"
 #TESTS_CPP="$(find tests -name '*.cpp')"
 
-OUTDIR=bin
-OBJDIR=obj
-PRE_TASK_SCRIPT=tasks/pre_build.sh
-POST_TASK_SCRIPT=
+# OBJDIR structure:
+#  ├── objects  - dir where compiled *.o files are stored. cleans every call of build task
+#  ├── profile  - dir where gcc *.gcda profiling info files stored
+#  ├── libs     - there you can put static libs and linker will find them
+#  └── out      - output files are created here and then copied to OUTDIR
+OBJDIR="obj"
+OUTDIR="bin"
 
-case $OS in
+# OS-specific options
+case "$OS" in
     WINDOWS)
-        EXEC_FILE=$PROJECT.exe
+        EXEC_FILE="$PROJECT.exe"
+        SHARED_LIB_FILE="$PROJECT.dll"
         ;;
     LINUX)
-        EXEC_FILE=$PROJECT
+        EXEC_FILE="$PROJECT"
         ;;
     *)
-        printf "${RED}operating system $OS has no configuration variants\n"
-        exit 1
+        error "operating system $OS has no configuration variants"
         ;;
 esac
 
-case $TASK in
-    build_exec)
-        C_ARGS="-O2"
+# TASKS
+case "$TASK" in
+    rebuild_kerep)
+        TASK_SCRIPT=tasks/rebuild_kerep.sh
+        ;;
+    # generates different profile info
+    build_profile)
+        OUTDIR="$OUTDIR/profile"
+        # -flto applies more optimizations across object files
+        # -flto=auto is needed to multithreaded copilation
+        # -fuse-linker-plugin is required to use static libs with lto, it strips away all
+        # -pg adds code to executable, that generates file containing function call info (gmon.out)
+        # -fprofile-generate 
+        C_ARGS="-O2 -flto=auto -fuse-linker-plugin -pg -fprofile-generate -fprofile-prefix-path=$(realpath $OBJDIR)/objects"
         CPP_ARGS="$C_ARGS"
-        LINKER_ARGS=""
+        LINKER_ARGS="$CPP_ARGS"
+        PRE_TASK_SCRIPT=tasks/pre_build.sh
+        TASK_SCRIPT=cbuild/default_tasks/build_exec.sh
+        POST_TASK_SCRIPT=cbuild/default_tasks/profile.sh
+        KEREP_BUILD_TASK=build_static_lib
+        ;;
+    # creates executable using profile info generated by build_profile
+    build_exec)
+        # -flto applies more optimizations across object files
+        # -flto=auto is needed to multithreaded copilation
+        # -fuse-linker-plugin is required to use static libs with lto, it strips away all
+        C_ARGS="-O2 -flto=auto -fuse-linker-plugin -fprofile-use -fprofile-prefix-path=$(realpath $OBJDIR)/objects"
+        CPP_ARGS="$C_ARGS"
+        LINKER_ARGS="$CPP_ARGS"
+        PRE_TASK_SCRIPT=tasks/pre_build.sh
         TASK_SCRIPT=cbuild/default_tasks/build_exec.sh
         KEREP_BUILD_TASK=build_static_lib
         ;;
+    # creates executable with debug info and no optimizations
     build_exec_dbg)
         C_ARGS="-O0 -g"
         CPP_ARGS="$C_ARGS"
-        LINKER_ARGS=""
+        LINKER_ARGS="$CPP_ARGS"
+        PRE_TASK_SCRIPT=tasks/pre_build.sh
         TASK_SCRIPT=cbuild/default_tasks/build_exec.sh
         KEREP_BUILD_TASK=build_static_lib_dbg
         ;;
+    # executes $EXEC_FILE
     exec)
         TASK_SCRIPT=cbuild/default_tasks/exec.sh
         ;;
+    # executes $EXEC_FILE with valgrind memory checker
     valgrind)  
         VALGRIND_ARGS="-s --log-file=valgrind.log --read-var-info=yes --track-origins=yes --fullpath-after=$PROJECT/ --leak-check=full --show-leak-kinds=all" 
         TASK_SCRIPT=cbuild/default_tasks/valgrind.sh
         ;;
+    # deletes generated files
+    clean)
+        TASK_SCRIPT=cbuild/default_tasks/clean.sh
+        ;;
+    # unknown task
+    *)
+        error "task <$TASK> not found"
+    ;;
 esac
diff --git a/kerep b/kerep
index d2eb241..dbf2c27 160000
--- a/kerep
+++ b/kerep
@@ -1 +1 @@
-Subproject commit d2eb241d0df5c88958888afa9f577c3dd1414d21
+Subproject commit dbf2c2772c832bbb6f8f56b9741a21722daa01a2
diff --git a/tasks/clean_additions.sh b/tasks/clean_additions.sh
new file mode 100644
index 0000000..85a607e
--- /dev/null
+++ b/tasks/clean_additions.sh
@@ -0,0 +1,4 @@
+#!/usr/bin/bash
+
+myprint "${WHITE}deleting .kerep_rebuild.tmp"
+rm -rf .kerep_rebuild.tmp
diff --git a/tasks/pre_build.sh b/tasks/pre_build.sh
index 4f3a298..60439dd 100644
--- a/tasks/pre_build.sh
+++ b/tasks/pre_build.sh
@@ -1,13 +1,17 @@
 #!/bin/bash
 
-if [ ! -f "kerep/bin/kerep.a" ]  || [ -f .rebuild_kerep ] 
-then
+# check if kerep static lib exists or kerep_rebuild task was executed
+if [ ! -f "$OBJDIR/libs/kerep.a" ] || [ -f .rebuild_kerep.tmp ]; then
+    [[ -z "$KEREP_BUILD_TASK" ]] && error "KEREP_BUILD_TASK is empty" 
+    myprint "${BLUE}making kerep task <$KEREP_BUILD_TASK>"
+
     cd kerep
     if ! make "$KEREP_BUILD_TASK"; then
         exit 1
     fi
     cd ..
-    rm -rf .rebuild_kerep
+
+    cp kerep/bin/kerep.a $OBJDIR/libs/
+    myprint "${GREEN}copied ${CYAN}kerep.a"
+    rm .rebuild_kerep.tmp
 fi
-cp kerep/bin/kerep.a obj/
-printf "${GREEN}copied ${CYAN}kerep.a\n"
diff --git a/tasks/rebuild_kerep.sh b/tasks/rebuild_kerep.sh
index ea7e93b..7698a61 100644
--- a/tasks/rebuild_kerep.sh
+++ b/tasks/rebuild_kerep.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
-touch .rebuild_kerep
-printf "kerep.a will be rebuilt in the next build task"
+touch .rebuild_kerep.tmp
+myprint "${YELLOW}kerep.a will be rebuilt in the next build task"