clang: make code submissive and debuggable

CMakeLists.txt

@@ -23,8 +23,15 @@ include("arch/${ARCH}/config/toolchain.cmake")
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -ffreestanding")
 set(CMAKE_ASM_FLAGS "${CMAKE_ASM_FLAGS} -D_ASM_SOURCE")
 if(DEBUG)
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Og -ggdb")
-    set(CMAKE_ASM_FLAGS "${CMAKE_ASM_FLAGS} -Og -ggdb")
+    # -Og on gcc optimizes for the best debugging experience, but apparently this
+    # is treated the same as -O1 on clang for some reason.  The LLVM manual says
+    # you're supposed to use -O0 in order to get the most submissive and debuggable
+    # code instead:
+    # <https://clang.llvm.org/docs/CommandGuide/clang.html#code-generation-options>
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -O0 -ggdb")
+    # i don't think -O0 does anything for assembly code, but it can't hurt to
+    # have it in there just in case (somebody check on this at some point plz)
+    set(CMAKE_ASM_FLAGS "${CMAKE_ASM_FLAGS} -O0 -ggdb")
 else()
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -O2")
 endif()