Test cpp_dummy_build in pedantic mode

In public headers, we want to avoid things that are not standard C++,
including features that GCC and Clang support as extensions, such as
flexible array members. So compile with `-pedantic`.

Non-regression for #9020.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

CMakeLists.txt

@@ -281,6 +281,15 @@ if(MBEDTLS_FATAL_WARNINGS)
     endif(CMAKE_COMPILER_IS_IAR)
 endif(MBEDTLS_FATAL_WARNINGS)
 
+if(CMAKE_BUILD_TYPE STREQUAL "Check" AND TEST_CPP)
+    set(CMAKE_CXX_STANDARD 11)
+    set(CMAKE_CXX_STANDARD_REQUIRED ON)
+    set(CMAKE_CXX_EXTENSIONS OFF)
+    if(CMAKE_COMPILER_IS_CLANG OR CMAKE_COMPILER_IS_GNU)
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pedantic")
+    endif()
+endif()
+
 if(CMAKE_BUILD_TYPE STREQUAL "Coverage")
     if(CMAKE_COMPILER_IS_GNU OR CMAKE_COMPILER_IS_CLANG)
         set(CMAKE_SHARED_LINKER_FLAGS "--coverage")

scripts/common.make

@@ -20,7 +20,7 @@ include $(MBEDTLS_PATH)/framework/exported.make
 
 CFLAGS	?= -O2
 WARNING_CFLAGS ?= -Wall -Wextra -Wformat=2 -Wno-format-nonliteral
-WARNING_CXXFLAGS ?= -Wall -Wextra -Wformat=2 -Wno-format-nonliteral
+WARNING_CXXFLAGS ?= -Wall -Wextra -Wformat=2 -Wno-format-nonliteral -std=c++11 -pedantic
 LDFLAGS ?=
 
 LOCAL_CFLAGS = $(WARNING_CFLAGS) -I$(MBEDTLS_TEST_PATH)/include \

tests/scripts/all.sh

@@ -5053,7 +5053,7 @@ component_test_psa_crypto_drivers () {
 
 component_test_make_shared () {
     msg "build/test: make shared" # ~ 40s
-    make SHARED=1 all check
+    make SHARED=1 TEST_CPP=1 all check
     ldd programs/util/strerror | grep libmbedcrypto
     programs/test/dlopen_demo.sh
 }
@@ -5838,7 +5838,7 @@ component_test_cmake_out_of_source () {
     mkdir "$OUT_OF_SOURCE_DIR"
     cd "$OUT_OF_SOURCE_DIR"
     # Note: Explicitly generate files as these are turned off in releases
-    cmake -D CMAKE_BUILD_TYPE:String=Check -D GEN_FILES=ON "$MBEDTLS_ROOT_DIR"
+    cmake -D CMAKE_BUILD_TYPE:String=Check -D GEN_FILES=ON -D TEST_CPP=1 "$MBEDTLS_ROOT_DIR"
     make
 
     msg "test: cmake 'out-of-source' build"