Run C regression tests using clang and gcc when both are available

Our C front-end seeks to conform to whatever interpretation of the C
standard the underlying host C compiler has. To avoid incompatibilities
as documented in diffblue#2370, run regression tests using both Clang and GCC,
if available on a particular system.

Author: tautschnig

regression/ansi-c/CMakeLists.txt

@@ -19,9 +19,32 @@ elseif("${CMAKE_SYSTEM_NAME}" STREQUAL "Darwin")
         "CORE"
     )
 else()
+    find_program(CLANG_EXISTS "clang")
+    find_program(GCC_EXISTS "gcc")
+    if(CLANG_EXISTS AND GCC_EXISTS)
+    add_test_pl_profile(
+        "ansi-c-clang"
+        "$<TARGET_FILE:goto-cc> --native-compiler clang"
+        "-C;-s;ansi-c-clang"
+        "CORE"
+    )
+    add_test_pl_profile(
+        "ansi-c-gcc"
+        "$<TARGET_FILE:goto-cc> --native-compiler gcc"
+        "-C;-X;fake-gcc-version;-s;ansi-c-gcc"
+        "CORE"
+    )
+    add_test_pl_profile(
+        "ansi-c-fake-gcc"
+        "$<TARGET_FILE:goto-cc>"
+        "-C;-I;fake-gcc-version;-s;ansi-c-fake-gcc"
+        "CORE"
+    )
+    else()
     add_test_pl_tests(
         "$<TARGET_FILE:goto-cc>"
     )
+    endif()
 
     add_test_pl_profile(
         "ansi-c-c++-front-end"

regression/ansi-c/Makefile

@@ -23,13 +23,25 @@ endif
 endif
 
 test:
-	@../test.pl -e -p -c $(exe) $(excluded_tests)
+	if which gcc && which clang ; then \
+	  ../test.pl -e -p -c "$(exe) --native-compiler clang" $(excluded_tests) && \
+	  ../test.pl -e -p -c "$(exe) --native-compiler gcc" $(excluded_tests) -X fake-gcc-version && \
+	  ../test.pl -e -p -c $(exe) $(excluded_tests) -I fake-gcc-version ; \
+	else \
+	  ../test.pl -e -p -c $(exe) $(excluded_tests) ; \
+	fi
 ifneq ($(BUILD_ENV_),MSVC)
 	@../test.pl -e -p -c "$(exe) -xc++ -D_Bool=bool" -I test-c++-front-end -s c++-front-end $(excluded_tests)
 endif
 
 tests.log: ../test.pl
-	@../test.pl -e -p -c $(exe) $(excluded_tests)
+	if which gcc && which clang ; then \
+	  ../test.pl -e -p -c "$(exe) --native-compiler clang" $(excluded_tests) && \
+	  ../test.pl -e -p -c "$(exe) --native-compiler gcc" $(excluded_tests) -X fake-gcc-version && \
+	  ../test.pl -e -p -c $(exe) $(excluded_tests) -I fake-gcc-version ; \
+	else \
+	  ../test.pl -e -p -c $(exe) $(excluded_tests) ; \
+	fi
 ifneq ($(BUILD_ENV_),MSVC)
 	@../test.pl -e -p -c "$(exe) -xc++ -D_Bool=bool" -I test-c++-front-end -s c++-front-end $(excluded_tests)
 endif

regression/ansi-c/gcc_version1/test-gcc-4.desc

@@ -1,4 +1,4 @@
-CORE gcc-only
+CORE gcc-only fake-gcc-version
 gcc-4.c
 --native-compiler ./fake-gcc-4
 ^EXIT=0$

regression/ansi-c/gcc_version1/test-gcc-5.desc

@@ -1,4 +1,4 @@
-CORE gcc-only
+CORE gcc-only fake-gcc-version
 gcc-5.c
 --native-compiler ./fake-gcc-5
 ^EXIT=0$

regression/ansi-c/gcc_version1/test-gcc-7.desc

@@ -1,4 +1,4 @@
-CORE gcc-only
+CORE gcc-only fake-gcc-version
 gcc-7.c
 --native-compiler ./fake-gcc-7
 ^EXIT=0$