Introduce valgrind to the CI pipeline

The static analyzer alone can't catch all the runtime issues. In this
commit, the dynamic analysis tool Valgrind is added to the CI pipeline.

ENABLE_SDL is set to 0, in order to reduce noise caused by the external
libraries.

Reference:
- https://valgrind.org/docs/manual/quick-start.html
- https://linux.die.net/man/1/gcc

.github/workflows/main.yml

@@ -42,7 +42,7 @@ jobs:
     - name: install-dependencies
       run: |
             sudo apt-get update -q -y
-            sudo apt-get install -q -y libsdl2-dev libsdl2-mixer-dev
+            sudo apt-get install -q -y libsdl2-dev libsdl2-mixer-dev valgrind
             .ci/riscv-toolchain-install.sh
       shell: bash
     - name: default build
@@ -73,6 +73,16 @@ jobs:
       run: |
             make clean && make ENABLE_UBSAN=1 check -j$(nproc)
             make clean && make ENABLE_JIT=1 ENABLE_UBSAN=1 check -j$(nproc)
+    - name: valgrind check (without JIT)
+      run: |
+            make clean && make ENABLE_SDL=0 ENABLE_JIT=0 ENABLE_VALGRIND=1
+            valgrind --leak-check=full --show-leak-kinds=all --error-exitcode=1 ./build/rv32emu ./build/hello.elf 
+            valgrind --leak-check=full --show-leak-kinds=all --error-exitcode=1 ./build/rv32emu ./build/aes.elf 
+    - name: valgrind check (with JIT)
+      run: |
+            make clean && make ENABLE_SDL=0 ENABLE_JIT=1 ENABLE_VALGRIND=1
+            valgrind --leak-check=full --show-leak-kinds=all --error-exitcode=1 ./build/rv32emu ./build/hello.elf 
+            valgrind --leak-check=full --show-leak-kinds=all --error-exitcode=1 ./build/rv32emu ./build/aes.elf 
 
   host-arm64:
     needs: [detect-code-related-file-changes]

Makefile

@@ -11,6 +11,14 @@ CFLAGS = -std=gnu99 -O2 -Wall -Wextra
 CFLAGS += -Wno-unused-label
 CFLAGS += -include src/common.h
 
+ENABLE_VALGRIND ?= 0
+ifeq ("$(ENABLE_UBSAN)", "1")
+# according to gcc's man page: "If you use multiple -O options, with or without level numbers, the last such option is the one that is effective."
+# In order to use Valgrind, we need to compile with -g
+CFLAGS += -g
+LDFLAGS += -g
+endif
+
 # Enable link-time optimization (LTO)
 ENABLE_LTO ?= 1
 ifeq ($(call has, LTO), 1)