diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index dd4049358a..aff9bea8d1 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -37,6 +37,12 @@ build_template_app:
     # branch
     - git checkout ${CI_BUILD_REF_NAME} || echo "Using esp-idf-template default branch..."
     - make defconfig
+    # Test debug build (default)
+    - make all V=1
+    # Now test release build
+    - make clean
+    - sed -i.bak -e's/CONFIG_OPTIMIZATION_LEVEL_DEBUG\=y/CONFIG_OPTIMIZATION_LEVEL_RELEASE=y/' sdkconfig
+    - make defconfig
     - make all V=1
 
 
diff --git a/Kconfig b/Kconfig
index 11ea099de2..deb0cea839 100644
--- a/Kconfig
+++ b/Kconfig
@@ -23,6 +23,26 @@ endmenu
 
 source "$COMPONENT_KCONFIGS_PROJBUILD"
 
+choice OPTIMIZATION_LEVEL
+    prompt "Optimization level"
+    default OPTIMIZATION_LEVEL_DEBUG
+    help
+        This option sets optimization level.
+        
+        - for "Release" setting, -Os flag is added to CFLAGS,
+         and -DNDEBUG flag is added to CPPFLAGS.
+         
+        - for "Debug" setting, -Og flag is added to CFLAGS.
+        
+        To override any of these settings, set CFLAGS and/or CPPFLAGS
+        in project makefile, before including $(IDF_PATH)/make/project.mk.
+        
+config OPTIMIZATION_LEVEL_DEBUG
+    bool "Debug"
+config OPTIMIZATION_LEVEL_RELEASE
+    bool "Release"
+endchoice
+
 menu "Component config"
 source "$COMPONENT_KCONFIGS"
 endmenu
diff --git a/components/log/log.c b/components/log/log.c
index aae12a7735..a2b41d7e62 100644
--- a/components/log/log.c
+++ b/components/log/log.c
@@ -284,7 +284,7 @@ static inline void heap_swap(int i, int j)
 }
 #endif //BOOTLOADER_BUILD
 
-inline IRAM_ATTR uint32_t esp_log_early_timestamp()
+IRAM_ATTR uint32_t esp_log_early_timestamp()
 {
     return xthal_get_ccount() / (CPU_CLK_FREQ_ROM / 1000);
 }
diff --git a/components/nghttp/library/nghttp2_session.c b/components/nghttp/library/nghttp2_session.c
index f93cd1729b..0100dd32c4 100644
--- a/components/nghttp/library/nghttp2_session.c
+++ b/components/nghttp/library/nghttp2_session.c
@@ -7177,7 +7177,7 @@ uint32_t nghttp2_session_get_remote_settings(nghttp2_session *session,
     return session->remote_settings.max_header_list_size;
   }
 
-  assert(0);
+  abort();
 }
 
 static int nghttp2_session_upgrade_internal(nghttp2_session *session,
diff --git a/components/nvs_flash/src/nvs_page.cpp b/components/nvs_flash/src/nvs_page.cpp
index 4f6a198c61..f4fc5430cd 100644
--- a/components/nvs_flash/src/nvs_page.cpp
+++ b/components/nvs_flash/src/nvs_page.cpp
@@ -769,7 +769,7 @@ void Page::invalidateCache()
 
 void Page::debugDump() const
 {
-    printf("state=%x addr=%x seq=%d\nfirstUsed=%d nextFree=%d used=%d erased=%d\n", mState, mBaseAddress, mSeqNumber, static_cast<int>(mFirstUsedEntry), static_cast<int>(mNextFreeEntry), mUsedEntryCount, mErasedEntryCount);
+    printf("state=%x addr=%x seq=%d\nfirstUsed=%d nextFree=%d used=%d erased=%d\n", (int) mState, mBaseAddress, mSeqNumber, static_cast<int>(mFirstUsedEntry), static_cast<int>(mNextFreeEntry), mUsedEntryCount, mErasedEntryCount);
     size_t skip = 0;
     for (size_t i = 0; i < ENTRY_COUNT; ++i) {
         printf("%3d: ", static_cast<int>(i));
diff --git a/components/nvs_flash/src/nvs_pagemanager.cpp b/components/nvs_flash/src/nvs_pagemanager.cpp
index 790ab7e19f..f4d02a7d40 100644
--- a/components/nvs_flash/src/nvs_pagemanager.cpp
+++ b/components/nvs_flash/src/nvs_pagemanager.cpp
@@ -49,7 +49,7 @@ esp_err_t PageManager::load(uint32_t baseSector, uint32_t sectorCount)
         return activatePage();
     } else {
         uint32_t lastSeqNo;
-        assert(mPageList.back().getSeqNumber(lastSeqNo) == ESP_OK);
+        ESP_ERROR_CHECK( mPageList.back().getSeqNumber(lastSeqNo) );
         mSeqNumber = lastSeqNo + 1;
     }
 
@@ -142,7 +142,9 @@ esp_err_t PageManager::requestNewPage()
     Page* newPage = &mPageList.back();
 
     Page* erasedPage = maxErasedItemsPageIt;
+#ifndef NDEBUG
     size_t usedEntries = erasedPage->getUsedEntryCount();
+#endif
     err = erasedPage->markFreeing();
     if (err != ESP_OK) {
         return err;
diff --git a/components/nvs_flash/src/nvs_storage.cpp b/components/nvs_flash/src/nvs_storage.cpp
index 4a217ebe18..eb90cac5bc 100644
--- a/components/nvs_flash/src/nvs_storage.cpp
+++ b/components/nvs_flash/src/nvs_storage.cpp
@@ -123,8 +123,7 @@ esp_err_t Storage::writeItem(uint8_t nsIndex, ItemType datatype, const char* key
     if (findPage) {
         if (findPage->state() == Page::PageState::UNINITIALIZED ||
                 findPage->state() == Page::PageState::INVALID) {
-            auto err = findItem(nsIndex, datatype, key, findPage, item);
-            assert(err == ESP_OK);
+            ESP_ERROR_CHECK( findItem(nsIndex, datatype, key, findPage, item) );
         }
         err = findPage->eraseItem(nsIndex, datatype, key);
         if (err == ESP_ERR_FLASH_OP_FAIL) {
diff --git a/make/component_common.mk b/make/component_common.mk
index ebad525a76..bf2eace019 100644
--- a/make/component_common.mk
+++ b/make/component_common.mk
@@ -91,15 +91,15 @@ define GenerateCompileTargets
 # $(1) - directory containing source files, relative to $(COMPONENT_PATH)
 $(1)/%.o: $$(COMPONENT_PATH)/$(1)/%.c | $(1)
 	$$(summary) CC $$@
-	$$(Q) $$(CC) $$(CFLAGS) $$(addprefix -I ,$$(COMPONENT_INCLUDES)) $$(addprefix -I ,$$(COMPONENT_EXTRA_INCLUDES)) -I$(1) -c $$< -o $$@
+	$$(Q) $$(CC) $$(CFLAGS) $(CPPFLAGS) $$(addprefix -I ,$$(COMPONENT_INCLUDES)) $$(addprefix -I ,$$(COMPONENT_EXTRA_INCLUDES)) -I$(1) -c $$< -o $$@
 
 $(1)/%.o: $$(COMPONENT_PATH)/$(1)/%.cpp | $(1)
-	$$(summary) CC $$@
-	$$(Q) $$(CXX) $$(CXXFLAGS) $$(addprefix -I,$$(COMPONENT_INCLUDES)) $$(addprefix -I,$$(COMPONENT_EXTRA_INCLUDES)) -I$(1) -c $$< -o $$@
+	$$(summary) CXX $$@
+	$$(Q) $$(CXX) $$(CXXFLAGS) $(CPPFLAGS) $$(addprefix -I,$$(COMPONENT_INCLUDES)) $$(addprefix -I,$$(COMPONENT_EXTRA_INCLUDES)) -I$(1) -c $$< -o $$@
 
 $(1)/%.o: $$(COMPONENT_PATH)/$(1)/%.S | $(1)
-	$$(summary) CC $$@
-	$$(Q) $$(CC) $$(CFLAGS) $$(addprefix -I ,$$(COMPONENT_INCLUDES)) $$(addprefix -I ,$$(COMPONENT_EXTRA_INCLUDES)) -I$(1) -c $$< -o $$@
+	$$(summary) AS $$@
+	$$(Q) $$(CC) $$(CFLAGS) $(CPPFLAGS) $$(addprefix -I ,$$(COMPONENT_INCLUDES)) $$(addprefix -I ,$$(COMPONENT_EXTRA_INCLUDES)) -I$(1) -c $$< -o $$@
 
 # CWD is build dir, create the build subdirectory if it doesn't exist
 $(1):
diff --git a/make/project.mk b/make/project.mk
index 2b2eff3f5e..2337bef1bc 100644
--- a/make/project.mk
+++ b/make/project.mk
@@ -151,23 +151,61 @@ LDFLAGS ?= -nostdlib \
 	-Wl,-EL
 
 # Set default CPPFLAGS, CFLAGS, CXXFLAGS
-#
 # These are exported so that components can use them when compiling.
-#
 # If you need your component to add CFLAGS/etc for it's own source compilation only, set CFLAGS += in your component's Makefile.
-#
 # If you need your component to add CFLAGS/etc globally for all source
-# files, set CFLAGS += in your component's Makefile.projbuild
+#  files, set CFLAGS += in your component's Makefile.projbuild
+# If you need to set CFLAGS/CPPFLAGS/CXXFLAGS at project level, set them in application Makefile
+#  before including project.mk. Default flags will be added before the ones provided in application Makefile.
 
-# CPPFLAGS used by an compile pass that uses the C preprocessor
-CPPFLAGS = -DESP_PLATFORM -Og -g3 -Wpointer-arith -Werror -Wno-error=unused-function -Wno-error=unused-but-set-variable \
-		-Wno-error=unused-variable -Wall -ffunction-sections -fdata-sections -mlongcalls -nostdlib -MMD -MP
+# CPPFLAGS used by C preprocessor
+# If any flags are defined in application Makefile, add them at the end. 
+CPPFLAGS := -DESP_PLATFORM $(CPPFLAGS)
 
-# C flags use by C only
-CFLAGS = $(CPPFLAGS) -std=gnu99 -g3 -fstrict-volatile-bitfields
+# Warnings-related flags relevant both for C and C++
+COMMON_WARNING_FLAGS = -Wall -Werror \
+	-Wno-error=unused-function \
+	-Wno-error=unused-but-set-variable \
+	-Wno-error=unused-variable 
 
-# CXXFLAGS uses by C++ only
-CXXFLAGS = $(CPPFLAGS) -Og -std=gnu++11 -g3 -fno-exceptions -fstrict-volatile-bitfields -fno-rtti
+# Flags which control code generation and dependency generation, both for C and C++
+COMMON_FLAGS = \
+	-ffunction-sections -fdata-sections \
+	-fstrict-volatile-bitfields \
+	-mlongcalls \
+	-nostdlib \
+	-MMD -MP
+
+# Optimization flags are set based on menuconfig choice
+ifneq ("$(CONFIG_OPTIMIZATION_LEVEL_RELEASE)","")
+OPTIMIZATION_FLAGS = -Os
+CPPFLAGS += -DNDEBUG
+else
+OPTIMIZATION_FLAGS = -Og
+endif
+
+# Enable generation of debugging symbols
+OPTIMIZATION_FLAGS += -ggdb
+
+# List of flags to pass to C compiler
+# If any flags are defined in application Makefile, add them at the end.
+CFLAGS := $(strip \
+	-std=gnu99 \
+	$(OPTIMIZATION_FLAGS) \
+	$(COMMON_FLAGS) \
+	$(COMMON_WARNING_FLAGS) \
+	$(CFLAGS))
+
+# List of flags to pass to C++ compiler
+# If any flags are defined in application Makefile, add them at the end.
+CXXFLAGS := $(strip \
+	-std=gnu++11 \
+	-fno-exceptions \
+	-fno-rtti \
+	$(OPTIMIZATION_FLAGS) \
+	$(COMMON_FLAGS) \
+	$(COMMON_WARNING_FLAGS) \
+	$(CXXFLAGS))
 
 export CFLAGS CPPFLAGS CXXFLAGS