diff --git a/.travis/script.sh b/.travis/script.sh
index bd39ba243..42667f96d 100755
--- a/.travis/script.sh
+++ b/.travis/script.sh
@@ -121,7 +121,7 @@ build_cc2538() {
     git checkout -- . || die
     git clean -xfd || die
     mkdir build && cd build || die
-    cmake -GNinja -DCMAKE_TOOLCHAIN_FILE=examples/platforms/cc2538/arm-none-eabi.cmake -DOT_PLATFORM=cc2538 .. || die
+    cmake -GNinja -DCMAKE_TOOLCHAIN_FILE=examples/platforms/cc2538/arm-none-eabi.cmake -DOT_PLATFORM=cc2538 -DOT_COMPILE_WARNING_AS_ERROR=ON .. || die
     ninja || die
     cd .. || die
 
@@ -419,7 +419,7 @@ build_samr21() {
     git checkout -- . || die
     git clean -xfd || die
     mkdir build && cd build || die
-    cmake -GNinja -DOT_PLATFORM=posix .. || die
+    cmake -GNinja -DOT_PLATFORM=posix -DOT_COMPILE_WARNING_AS_ERROR=ON .. || die
     ninja || die
     cd .. || die
 
@@ -586,14 +586,14 @@ build_samr21() {
     git checkout -- . || die
     git clean -xfd || die
     mkdir build && cd build || die
-    cmake -GNinja -DOT_PLATFORM=posix-host -DOT_DAEMON=ON .. || die
+    cmake -GNinja -DOT_PLATFORM=posix-host -DOT_DAEMON=ON -DCOMPILE_WARNING_AS_ERROR=ON .. || die
     ninja || die
     cd .. || die
 
     git checkout -- . || die
     git clean -xfd || die
     mkdir build && cd build || die
-    cmake -GNinja -DOT_PLATFORM=posix-host .. || die
+    cmake -GNinja -DOT_PLATFORM=posix-host -DCOMPILE_WARNING_AS_ERROR=ON .. || die
     ninja || die
     cd .. || die
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index e81b3fb75..61090712f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -36,6 +36,18 @@ include("${PROJECT_SOURCE_DIR}/etc/cmake/checks.cmake")
 include("${PROJECT_SOURCE_DIR}/etc/cmake/options.cmake")
 include("${PROJECT_SOURCE_DIR}/etc/cmake/functions.cmake")
 
+if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_C_COMPILER_ID MATCHES "(Apple)?[Cc]lang")
+    option(OT_COMPILE_WARNING_AS_ERROR "whether to include -Werror with gcc-compatible compilers")
+    if (OT_COMPILE_WARNING_AS_ERROR)
+        set(OT_CFLAGS -Werror)
+    endif()
+
+    set(OT_CFLAGS
+        $<$<COMPILE_LANGUAGE:C>:${OT_CFLAGS} -Wall -Wextra -Wshadow -Werror -pedantic-errors>
+        $<$<COMPILE_LANGUAGE:CXX>:${OT_FLAGS} -Wall -Wextra -Wshadow -Wno-c++14-compat -fno-exceptions>
+    )
+endif()
+
 file(READ .default-version OT_DEFAULT_VERSION)
 execute_process(
     COMMAND bash "-c" "third_party/nlbuild-autotools/repo/scripts/mkversion -b ${OT_DEFAULT_VERSION}"
diff --git a/examples/platforms/cc2538/CMakeLists.txt b/examples/platforms/cc2538/CMakeLists.txt
index 13ecedb0d..50fe9b357 100644
--- a/examples/platforms/cc2538/CMakeLists.txt
+++ b/examples/platforms/cc2538/CMakeLists.txt
@@ -55,12 +55,18 @@ add_library(openthread-cc2538
     $<TARGET_OBJECTS:openthread-platform-utils>
 )
 
+set_property(TARGET openthread-cc2538 PROPERTY C_STANDARD 99)
+
 target_link_libraries(openthread-cc2538 PRIVATE openthread-platform-utils)
 target_link_options(openthread-cc2538 PUBLIC -T${PROJECT_SOURCE_DIR}/examples/platforms/cc2538/cc2538.ld)
 target_link_options(openthread-cc2538 PUBLIC -Wl,-Map=$<TARGET_PROPERTY:NAME>.map)
 
 target_compile_definitions(openthread-cc2538 PUBLIC ${OT_PLATFORM_DEFINES})
 
+target_compile_options(openthread-cc2538 PRIVATE
+    ${OT_CFLAGS}
+)
+
 target_include_directories(openthread-cc2538 PRIVATE
     ${OT_PUBLIC_INCLUDES}
     ${OT_PRIVATE_INCLUDES}
diff --git a/examples/platforms/posix/CMakeLists.txt b/examples/platforms/posix/CMakeLists.txt
index b4d7229e6..50301944b 100644
--- a/examples/platforms/posix/CMakeLists.txt
+++ b/examples/platforms/posix/CMakeLists.txt
@@ -34,6 +34,8 @@ if(NOT OT_CONFIG)
 endif()
 
 list(APPEND OT_PLATFORM_DEFINES
+    "_BSD_SOURCE=1"
+    "_DEFAULT_SOURCE=1"
     "OPENTHREAD_EXAMPLES_POSIX=1"
     "OPENTHREAD_POSIX=1"
     "OPENTHREAD_CONFIG_NCP_UART_ENABLE=1"
@@ -58,6 +60,8 @@ add_library(openthread-posix
     $<TARGET_OBJECTS:openthread-platform-utils>
 )
 
+set_property(TARGET openthread-posix PROPERTY C_STANDARD 99)
+
 find_library(LIBRT rt)
 if(LIBRT)
     target_link_libraries(openthread-posix PRIVATE ${LIBRT})
@@ -67,6 +71,10 @@ target_link_libraries(openthread-posix PRIVATE openthread-platform-utils)
 
 target_compile_definitions(openthread-posix PUBLIC ${OT_PLATFORM_DEFINES})
 
+target_compile_options(openthread-posix PRIVATE
+    ${OT_CFLAGS}
+)
+
 target_include_directories(openthread-posix PRIVATE
     ${OT_PUBLIC_INCLUDES}
     ${OT_PRIVATE_INCLUDES}
diff --git a/src/cli/CMakeLists.txt b/src/cli/CMakeLists.txt
index 33c9d9ec5..55dc8b785 100644
--- a/src/cli/CMakeLists.txt
+++ b/src/cli/CMakeLists.txt
@@ -29,6 +29,13 @@
 add_library(openthread-cli-ftd)
 add_library(openthread-cli-mtd)
 
+set_target_properties(
+    openthread-cli-ftd openthread-cli-mtd
+    PROPERTIES
+        C_STANDARD 99
+        CXX_STANDARD 98
+)
+
 target_compile_definitions(openthread-cli-ftd PRIVATE
     ${OT_PRIVATE_DEFINES}
     OPENTHREAD_FTD=1
@@ -39,6 +46,14 @@ target_compile_definitions(openthread-cli-mtd PRIVATE
     OPENTHREAD_MTD=1
 )
 
+target_compile_options(openthread-cli-ftd PRIVATE
+    ${OT_CFLAGS}
+)
+
+target_compile_options(openthread-cli-mtd PRIVATE
+    ${OT_CFLAGS}
+)
+
 set(COMMON_INCLUDES
     ${OT_PRIVATE_INCLUDES}
     ${PROJECT_SOURCE_DIR}/src
diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 99c58cdea..848ae7294 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -30,6 +30,13 @@ add_library(openthread-ftd)
 add_library(openthread-mtd)
 add_library(openthread-radio)
 
+set_target_properties(
+    openthread-ftd openthread-mtd openthread-radio
+    PROPERTIES
+        C_STANDARD 99
+        CXX_STANDARD 98
+)
+
 target_compile_definitions(openthread-ftd PRIVATE
     ${OT_PRIVATE_DEFINES}
     OPENTHREAD_FTD=1
@@ -45,6 +52,18 @@ target_compile_definitions(openthread-radio PRIVATE
     OPENTHREAD_RADIO=1
 )
 
+target_compile_options(openthread-ftd PRIVATE
+    ${OT_CFLAGS}
+)
+
+target_compile_options(openthread-mtd PRIVATE
+    ${OT_CFLAGS}
+)
+
+target_compile_options(openthread-radio PRIVATE
+    ${OT_CFLAGS}
+)
+
 set(COMMON_INCLUDES
     ${OT_PRIVATE_INCLUDES}
     ${PROJECT_SOURCE_DIR}/src/core
diff --git a/src/ncp/CMakeLists.txt b/src/ncp/CMakeLists.txt
index e45ffb040..7d0836bab 100644
--- a/src/ncp/CMakeLists.txt
+++ b/src/ncp/CMakeLists.txt
@@ -30,6 +30,14 @@ add_library(openthread-ncp-ftd)
 add_library(openthread-ncp-mtd)
 add_library(openthread-rcp)
 
+# We depend on C++11 to validate that NCP handlers are sorted.
+set_target_properties(
+    openthread-ncp-mtd openthread-rcp
+    PROPERTIES
+        C_STANDARD 99
+        CXX_STANDARD 98
+)
+
 target_compile_definitions(openthread-ncp-ftd PRIVATE
     ${OT_PRIVATE_DEFINES}
     OPENTHREAD_FTD=1
@@ -48,6 +56,18 @@ target_compile_definitions(openthread-rcp PRIVATE
     OPENTHREAD_CONFIG_NCP_UART_ENABLE=1
 )
 
+target_compile_options(openthread-ncp-ftd PRIVATE
+    ${OT_CFLAGS}
+)
+
+target_compile_options(openthread-ncp-mtd PRIVATE
+    ${OT_CFLAGS}
+)
+
+target_compile_options(openthread-rcp PRIVATE
+    ${OT_CFLAGS}
+)
+
 set(COMMON_INCLUDES
     ${OT_PRIVATE_INCLUDES}
     ${PROJECT_SOURCE_DIR}/src
diff --git a/src/posix/CMakeLists.txt b/src/posix/CMakeLists.txt
index 920584f9b..446d342da 100644
--- a/src/posix/CMakeLists.txt
+++ b/src/posix/CMakeLists.txt
@@ -44,6 +44,10 @@ if(OT_DAEMON)
         OPENTHREAD_POSIX_APP_TYPE=2
     )
 
+    target_compile_options(ot-daemon PRIVATE
+        ${OT_CFLAGS}
+    )
+
     target_link_libraries(ot-daemon PRIVATE
         openthread-cli-ftd
         ${OT_PLATFORM_LIB}
@@ -57,6 +61,10 @@ if(OT_DAEMON)
         client.c
     )
 
+    target_compile_options(ot-ctl PRIVATE
+        ${OT_CFLAGS}
+    )
+
     target_include_directories(ot-ctl PRIVATE ${COMMON_INCLUDES})
 else()
     add_executable(ot-cli
@@ -69,6 +77,10 @@ else()
         OPENTHREAD_POSIX_APP_TYPE=2
     )
 
+    target_compile_options(ot-cli PRIVATE
+        ${OT_CFLAGS}
+    )
+
     target_link_libraries(ot-cli
         openthread-cli-ftd
         ${OT_PLATFORM_LIB}
@@ -81,12 +93,17 @@ else()
     add_executable(ot-ncp
         main.c
     )
+
     target_include_directories(ot-ncp PRIVATE ${COMMON_INCLUDES})
 
     target_compile_definitions(ot-ncp PRIVATE
         OPENTHREAD_POSIX_APP_TYPE=1
     )
 
+    target_compile_options(ot-ncp PRIVATE
+        ${OT_CFLAGS}
+    )
+
     target_link_libraries(ot-ncp
         openthread-ncp-ftd
         ${OT_PLATFORM_LIB}
diff --git a/src/posix/platform/CMakeLists.txt b/src/posix/platform/CMakeLists.txt
index 6cdc73e45..d1676b48b 100644
--- a/src/posix/platform/CMakeLists.txt
+++ b/src/posix/platform/CMakeLists.txt
@@ -64,6 +64,10 @@ target_link_libraries(openthread-posix PUBLIC
 
 target_compile_definitions(openthread-posix PUBLIC ${OT_PLATFORM_DEFINES})
 
+target_compile_options(openthread-posix PRIVATE
+    ${OT_CFLAGS}
+)
+
 target_include_directories(openthread-posix PRIVATE
     ${OT_PUBLIC_INCLUDES}
     ${OT_PRIVATE_INCLUDES}