cmake: override build system release optimization policy

The cmake config on the build system actually decides the release build optimization policy.
On Fedora, it's -O2.  On Ubuntu, it's -O3.

Anything given in CMakeLists.txt is overridden by the build system policy since it goes at
the end of the compiler commandline.

When you are building cross, the build system's opinion of your cross binary optimization
level is irrelevant, and at worst destructive.  Some versions of gcc contain broken optimizations
that are applied only at -O3.

This patch removes any doomed attempt to set -O in CMakeLists.txt, which has
no effect since the build system policy is still added at the end, but
removes confusion; and adds code to all the cross build files to forcibly
override release optimization level to -O2, removing the build system's
opinion of how your cross build should look.

CMakeLists.txt

@@ -1330,18 +1330,13 @@ if (CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX OR (CMAKE_C_COMPILER_ID
                 set(VISIBILITY_FLAG -fvisibility=hidden)
     endif()
     if (LWS_WITH_GCOV)
-	    set (GCOV_FLAGS "-fprofile-arcs -ftest-coverage -O0")
+	    set (GCOV_FLAGS "-fprofile-arcs -ftest-coverage ")
     endif()
 
 	if (LWS_WITH_ASAN)
 		set (ASAN_FLAGS "-fsanitize=address -fsanitize=pointer-compare -fsanitize=pointer-subtract -fsanitize=leak -fsanitize=undefined -fsanitize-address-use-after-scope -fsanitize-undefined-trap-on-error")
 		message("Enabling ASAN")
 	endif()
-    if (CMAKE_BUILD_TYPE MATCHES "DEBUG")
-		set(CMAKE_C_FLAGS "-O0 ${CMAKE_C_FLAGS}")
-    else()
-		set(CMAKE_C_FLAGS "-O3 ${CMAKE_C_FLAGS}")
-    endif()
 
     if (UNIX AND NOT LWS_WITH_ESP32)
 	    set(CMAKE_C_FLAGS "-Wall -Wsign-compare -Wignored-qualifiers -Wtype-limits -Wuninitialized -Werror ${VISIBILITY_FLAG} -Wundef ${GCOV_FLAGS} ${CMAKE_C_FLAGS} ${ASAN_FLAGS}" )

contrib/cross-aarch64.cmake

@@ -14,6 +14,22 @@ set(CMAKE_SYSTEM_PROCESSOR aarch64)
 set(CMAKE_C_COMPILER "aarch64-linux-gnu-gcc")
 set(CMAKE_CXX_COMPILER "aarch64-linux-gnu-g++")
 
+#
+# Different build system distros set release optimization level to different
+# things according to their local policy, eg, Fedora is -O2 and Ubuntu is -O3
+# here.  Actually the build system's local policy is completely unrelated to
+# our desire for cross-build release optimization policy for code built to run
+# on a completely different target than the build system itself.
+#
+# Since this goes last on the compiler commandline we have to override it to a
+# sane value for cross-build here.  Notice some gcc versions enable broken
+# optimizations with -O3.
+#
+if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
+	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE}" -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE}" -O2")
+endif()
+
 #-nostdlib
 SET(CMAKE_C_FLAGS "-DGCC_VER=\"\\\"$(GCC_VER)\\\"\" -DARM64=1 -D__LP64__=1 -Os -g3 -fpie -mstrict-align -DOPTEE_DEV_KIT=../../../../out/arm-plat-hikey/export-ta_arm64/include -I../../../../lib/libutee/include  -fPIC -ffunction-sections -fdata-sections -I../../../../core/include" CACHE STRING "" FORCE)
 

contrib/cross-arm-android-gnueabi.cmake

@@ -18,6 +18,22 @@ set(BUILD_SHARED_LIBS ON)
 set(CMAKE_C_COMPILER "${CROSS_PATH}/bin/arm-linux-androideabi-gcc")
 set(CMAKE_CXX_COMPILER "${CROSS_PATH}/bin/arm-linux-androideabi-g++")
 
+#
+# Different build system distros set release optimization level to different
+# things according to their local policy, eg, Fedora is -O2 and Ubuntu is -O3
+# here.  Actually the build system's local policy is completely unrelated to
+# our desire for cross-build release optimization policy for code built to run
+# on a completely different target than the build system itself.
+#
+# Since this goes last on the compiler commandline we have to override it to a
+# sane value for cross-build here.  Notice some gcc versions enable broken
+# optimizations with -O3.
+#
+if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
+	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE}" -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE}" -O2")
+endif()
+
 # Where to look for the target environment. (More paths can be added here)
 set(CMAKE_FIND_ROOT_PATH "${CROSS_PATH}")
 

contrib/cross-arm-linux-gnueabihf.cmake

@@ -15,6 +15,22 @@ set(CMAKE_SYSTEM_NAME Linux)
 set(CMAKE_C_COMPILER "${CROSS_PATH}/bin/arm-linux-gnueabihf-gcc")
 set(CMAKE_CXX_COMPILER "${CROSS_PATH}/bin/arm-linux-gnueabihf-g++")
 
+#
+# Different build system distros set release optimization level to different
+# things according to their local policy, eg, Fedora is -O2 and Ubuntu is -O3
+# here.  Actually the build system's local policy is completely unrelated to
+# our desire for cross-build release optimization policy for code built to run
+# on a completely different target than the build system itself.
+#
+# Since this goes last on the compiler commandline we have to override it to a
+# sane value for cross-build here.  Notice some gcc versions enable broken
+# optimizations with -O3.
+#
+if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
+	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE}" -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE}" -O2")
+endif()
+
 # Where to look for the target environment. (More paths can be added here)
 set(CMAKE_FIND_ROOT_PATH "${CROSS_PATH}")
 

contrib/cross-esp32.cmake

@@ -15,6 +15,22 @@ set(CMAKE_AR		"${CROSS_PATH}/bin/xtensa-esp32-elf-ar${EXECUTABLE_EXT}")
 set(CMAKE_RANLIB	"${CROSS_PATH}/bin/xtensa-esp32-elf-ranlib${EXECUTABLE_EXT}")
 set(CMAKE_LINKER	"${CROSS_PATH}/bin/xtensa-esp32-elf-ld${EXECUTABLE_EXT}")
 
+#
+# Different build system distros set release optimization level to different
+# things according to their local policy, eg, Fedora is -O2 and Ubuntu is -O3
+# here.  Actually the build system's local policy is completely unrelated to
+# our desire for cross-build release optimization policy for code built to run
+# on a completely different target than the build system itself.
+#
+# Since this goes last on the compiler commandline we have to override it to a
+# sane value for cross-build here.  Notice some gcc versions enable broken
+# optimizations with -O3.
+#
+if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
+	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE}" -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE}" -O2")
+endif()
+
 SET(CMAKE_C_FLAGS "-nostdlib -Wall -Werror \
 	-I${BUILD_DIR_BASE}/include \
 	-I${IDF_PATH}/components/newlib/platform_include \

contrib/cross-ming.cmake

@@ -18,6 +18,22 @@ set(CMAKE_C_COMPILER "${CROSS_PATH}/x86_64-w64-mingw32-gcc")
 set(CMAKE_RC_COMPILER "${CROSS_PATH}/x86_64-w64-mingw32-windres")
 set(CMAKE_C_FLAGS "-Wno-error")
 
+#
+# Different build system distros set release optimization level to different
+# things according to their local policy, eg, Fedora is -O2 and Ubuntu is -O3
+# here.  Actually the build system's local policy is completely unrelated to
+# our desire for cross-build release optimization policy for code built to run
+# on a completely different target than the build system itself.
+#
+# Since this goes last on the compiler commandline we have to override it to a
+# sane value for cross-build here.  Notice some gcc versions enable broken
+# optimizations with -O3.
+#
+if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
+	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE}" -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE}" -O2")
+endif()
+
 # Where to look for the target environment. (More paths can be added here)
 set(CMAKE_FIND_ROOT_PATH "${CROSS_PATH}")
 

contrib/cross-w32.cmake

@@ -17,6 +17,22 @@ set(CMAKE_CXX_COMPILER "${CROSS_PATH}/bin/i686-w64-mingw32-g++")
 set(CMAKE_RC_COMPILER "${CROSS_PATH}/bin/i686-w64-mingw32-windres")
 set(CMAKE_C_FLAGS "-Wno-error")
 
+#
+# Different build system distros set release optimization level to different
+# things according to their local policy, eg, Fedora is -O2 and Ubuntu is -O3
+# here.  Actually the build system's local policy is completely unrelated to
+# our desire for cross-build release optimization policy for code built to run
+# on a completely different target than the build system itself.
+#
+# Since this goes last on the compiler commandline we have to override it to a
+# sane value for cross-build here.  Notice some gcc versions enable broken
+# optimizations with -O3.
+#
+if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
+	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE}" -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE}" -O2")
+endif()
+
 # Where to look for the target environment. (More paths can be added here)
 set(CMAKE_FIND_ROOT_PATH "${CROSS_PATH}")
 

contrib/cross-w64.cmake

@@ -17,6 +17,22 @@ set(CMAKE_CXX_COMPILER "${CROSS_PATH}/bin/x86_64-w64-mingw32-g++")
 set(CMAKE_RC_COMPILER "${CROSS_PATH}/bin/x86_64-w64-mingw32-windres")
 set(CMAKE_C_FLAGS "-Wno-error")
 
+#
+# Different build system distros set release optimization level to different
+# things according to their local policy, eg, Fedora is -O2 and Ubuntu is -O3
+# here.  Actually the build system's local policy is completely unrelated to
+# our desire for cross-build release optimization policy for code built to run
+# on a completely different target than the build system itself.
+#
+# Since this goes last on the compiler commandline we have to override it to a
+# sane value for cross-build here.  Notice some gcc versions enable broken
+# optimizations with -O3.
+#
+if (CMAKE_BUILD_TYPE MATCHES RELEASE OR CMAKE_BUILD_TYPE MATCHES Release OR CMAKE_BUILD_TYPE MATCHES release)
+	set(CMAKE_C_FLAGS_RELEASE ${CMAKE_C_FLAGS_RELEASE}" -O2")
+	set(CMAKE_CXX_FLAGS_RELEASE ${CMAKE_CXX_FLAGS_RELEASE}" -O2")
+endif()
+
 # Where to look for the target environment. (More paths can be added here)
 set(CMAKE_FIND_ROOT_PATH "${CROSS_PATH}")