Disable -Wimplicit-fallthrough for funcs.generated.h

This is code generated by gperf, so there's nothing we can do about it.
The code does have /*FALLTHROUGH*/ comments but clang doesn't recognize
them.

CMakeLists.txt

@@ -267,8 +267,8 @@ else()
     -Wstrict-prototypes -std=gnu99 -Wshadow -Wconversion
     -Wmissing-prototypes)
 
-  check_c_compiler_flag(-Wimplicit-fallthrough HAS_WIMPLICIT_FALLTHROUGH_FLAG)
-  if(HAS_WIMPLICIT_FALLTHROUGH_FLAG)
+  check_c_compiler_flag(-Wimplicit-fallthrough HAVE_WIMPLICIT_FALLTHROUGH_FLAG)
+  if(HAVE_WIMPLICIT_FALLTHROUGH_FLAG)
     add_compile_options(-Wimplicit-fallthrough)
   endif()
 

config/config.h.in

@@ -60,5 +60,6 @@
 
 #cmakedefine HAVE_EXECINFO_BACKTRACE
 #cmakedefine HAVE_BUILTIN_ADD_OVERFLOW
+#cmakedefine HAVE_WIMPLICIT_FALLTHROUGH_FLAG
 
 #endif  // AUTO_CONFIG_H

src/nvim/eval/funcs.c

@@ -32,6 +32,7 @@
 #include "nvim/indent.h"
 #include "nvim/indent_c.h"
 #include "nvim/lua/executor.h"
+#include "nvim/macros.h"
 #include "nvim/mark.h"
 #include "nvim/math.h"
 #include "nvim/memline.h"
@@ -86,8 +87,10 @@ KHASH_MAP_INIT_STR(functions, VimLFuncDef)
 #endif
 
 PRAGMA_DIAG_PUSH_IGNORE_MISSING_PROTOTYPES
+PRAGMA_DIAG_PUSH_IGNORE_IMPLICIT_FALLTHROUGH
 #include "funcs.generated.h"
 PRAGMA_DIAG_POP
+PRAGMA_DIAG_POP
 #endif
 
 

src/nvim/macros.h

@@ -1,6 +1,8 @@
 #ifndef NVIM_MACROS_H
 #define NVIM_MACROS_H
 
+#include "auto/config.h"
+
 // EXTERN is only defined in main.c. That's where global variables are
 // actually defined and initialized.
 #ifndef EXTERN
@@ -203,16 +205,33 @@
 # define PRAGMA_DIAG_PUSH_IGNORE_MISSING_PROTOTYPES \
   _Pragma("clang diagnostic push") \
   _Pragma("clang diagnostic ignored \"-Wmissing-prototypes\"")
+# ifdef HAVE_WIMPLICIT_FALLTHROUGH_FLAG
+#  define PRAGMA_DIAG_PUSH_IGNORE_IMPLICIT_FALLTHROUGH \
+    _Pragma("clang diagnostic push") \
+    _Pragma("clang diagnostic ignored \"-Wimplicit-fallthrough\"")
+# else
+#  define PRAGMA_DIAG_PUSH_IGNORE_IMPLICIT_FALLTHROUGH \
+    _Pragma("clang diagnostic push")
+# endif
 # define PRAGMA_DIAG_POP \
     _Pragma("clang diagnostic pop")
 #elif defined(__GNUC__)
 # define PRAGMA_DIAG_PUSH_IGNORE_MISSING_PROTOTYPES \
   _Pragma("GCC diagnostic push") \
   _Pragma("GCC diagnostic ignored \"-Wmissing-prototypes\"")
+# ifdef HAVE_WIMPLICIT_FALLTHROUGH_FLAG
+#  define PRAGMA_DIAG_PUSH_IGNORE_IMPLICIT_FALLTHROUGH \
+    _Pragma("GCC diagnostic push") \
+    _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+# else
+#  define PRAGMA_DIAG_PUSH_IGNORE_IMPLICIT_FALLTHROUGH \
+    _Pragma("GCC diagnostic push")
+# endif
 # define PRAGMA_DIAG_POP \
   _Pragma("GCC diagnostic pop")
 #else
 # define PRAGMA_DIAG_PUSH_IGNORE_MISSING_PROTOTYPES
+# define PRAGMA_DIAG_PUSH_IGNORE_IMPLICIT_FALLTHROUGH
 # define PRAGMA_DIAG_POP
 #endif