chore: add additional compiler flags (#17815)

Added:
  - -Wdouble-promotion
  - -Wmissing-noreturn
  - -Wmissing-format-attribute
  - -Wsuggest-attribute={pure,const,malloc,cold}

Resolves: #343

CMakeLists.txt

@@ -284,6 +284,9 @@ if(MSVC)
 else()
   add_compile_options(-Wall -Wextra -pedantic -Wno-unused-parameter
     -Wstrict-prototypes -std=gnu99 -Wshadow -Wconversion
+    -Wdouble-promotion
+    -Wmissing-noreturn
+    -Wmissing-format-attribute
     -Wmissing-prototypes)
 
   check_c_compiler_flag(-Wimplicit-fallthrough HAVE_WIMPLICIT_FALLTHROUGH_FLAG)
@@ -291,6 +294,27 @@ else()
     add_compile_options(-Wimplicit-fallthrough)
   endif()
 
+  # Clang doesn't have -Wsuggest-attribute so check for each one.
+  check_c_compiler_flag(-Wsuggest-attribute=pure HAVE_WSUGGEST_ATTRIBUTE_PURE)
+  if(HAVE_WSUGGEST_ATTRIBUTE_PURE)
+    add_compile_options(-Wsuggest-attribute=pure)
+  endif()
+
+  check_c_compiler_flag(-Wsuggest-attribute=const HAVE_WSUGGEST_ATTRIBUTE_CONST)
+  if(HAVE_WSUGGEST_ATTRIBUTE_CONST)
+    add_compile_options(-Wsuggest-attribute=const)
+  endif()
+
+  check_c_compiler_flag(-Wsuggest-attribute=malloc HAVE_WSUGGEST_ATTRIBUTE_MALLOC)
+  if(HAVE_WSUGGEST_ATTRIBUTE_MALLOC)
+    add_compile_options(-Wsuggest-attribute=malloc)
+  endif()
+
+  check_c_compiler_flag(-Wsuggest-attribute=cold HAVE_WSUGGEST_ATTRIBUTE_COLD)
+  if(HAVE_WSUGGEST_ATTRIBUTE_COLD)
+    add_compile_options(-Wsuggest-attribute=cold)
+  endif()
+
   # On FreeBSD 64 math.h uses unguarded C11 extension, which taints clang
   # 3.4.1 used there.
   if(CMAKE_SYSTEM_NAME STREQUAL "FreeBSD" AND CMAKE_C_COMPILER_ID MATCHES "Clang")

src/nvim/CMakeLists.txt

@@ -182,12 +182,15 @@ foreach(sfile ${CONV_SOURCES})
     message(FATAL_ERROR "${sfile} doesn't exist (it was added to CONV_SOURCES)")
   endif()
 endforeach()
-# xdiff, mpack, lua-cjson: inlined external project, we don't maintain it. #9306
-list(APPEND CONV_SOURCES ${EXTERNAL_SOURCES})
 
 if(NOT MSVC)
   set_source_files_properties(
     ${CONV_SOURCES} PROPERTIES COMPILE_FLAGS "${COMPILE_FLAGS} -Wno-conversion")
+
+  # xdiff, mpack, lua-cjson: inlined external project, we don't maintain it. #9306
+  set_source_files_properties(
+    ${EXTERNAL_SOURCES} PROPERTIES COMPILE_FLAGS "${COMPILE_FLAGS} -Wno-conversion -Wno-missing-noreturn -Wno-missing-format-attribute -Wno-double-promotion")
+
   # gperf generates ANSI-C with incorrect linkage, ignore it.
   check_c_compiler_flag(-Wstatic-in-inline HAS_WSTATIC_IN_INLINE)
   if(HAS_WSTATIC_IN_INLINE)

src/nvim/eval.c

@@ -3976,18 +3976,11 @@ static int eval6(char_u **arg, typval_T *rettv, int evaluate, int want_string)
           f1 = f1 * f2;
         } else if (op == '/') {
           // Division by zero triggers error from AddressSanitizer
-          f1 = (f2 == 0
-                ? (
+          f1 = (f2 == 0 ? (
 #ifdef NAN
-                   f1 == 0
-                    ? NAN
-                    :
+              f1 == 0 ? (float_T)NAN :
 #endif
-                   (f1 > 0
-                     ? INFINITY
-                     : -INFINITY)
-                   )
-                     : f1 / f2);
+              (f1 > 0 ? (float_T)INFINITY : (float_T)-INFINITY)) : f1 / f2);
         } else {
           emsg(_("E804: Cannot use '%' with Float"));
           return FAIL;
@@ -5842,15 +5835,15 @@ size_t string2float(const char *const text, float_T *const ret_value)
 
   // MS-Windows does not deal with "inf" and "nan" properly
   if (STRNICMP(text, "inf", 3) == 0) {
-    *ret_value = INFINITY;
+    *ret_value = (float_T)INFINITY;
     return 3;
   }
   if (STRNICMP(text, "-inf", 3) == 0) {
-    *ret_value = -INFINITY;
+    *ret_value = (float_T)-INFINITY;
     return 4;
   }
   if (STRNICMP(text, "nan", 3) == 0) {
-    *ret_value = NAN;
+    *ret_value = (float_T)NAN;
     return 3;
   }
   *ret_value = strtod(text, &s);

src/nvim/ex_docmd.c

@@ -6629,6 +6629,7 @@ static void ex_quit(exarg_T *eap)
 
 /// ":cquit".
 static void ex_cquit(exarg_T *eap)
+  FUNC_ATTR_NORETURN
 {
   // this does not always pass on the exit code to the Manx compiler. why?
   getout(eap->addr_count > 0 ? (int)eap->line2 : EXIT_FAILURE);

src/nvim/log.c

@@ -282,6 +282,7 @@ static bool do_log_to_file(FILE *log_file, int log_level, const char *context,
 static bool v_do_log_to_file(FILE *log_file, int log_level, const char *context,
                              const char *func_name, int line_num, bool eol, const char *fmt,
                              va_list args)
+  FUNC_ATTR_PRINTF(7, 0)
 {
   static const char *log_levels[] = {
     [DEBUG_LOG_LEVEL]   = "DEBUG",

src/nvim/main.c

@@ -2099,6 +2099,7 @@ static bool file_owned(const char *fname)
 /// @param errstr  string containing an error message
 /// @param str     string to append to the primary error message, or NULL
 static void mainerr(const char *errstr, const char *str)
+  FUNC_ATTR_NORETURN
 {
   char *prgname = (char *)path_tail((char_u *)argv0);
 

src/nvim/os/input.c

@@ -522,6 +522,7 @@ static bool input_ready(MultiQueue *events)
 
 // Exit because of an input read error.
 static void read_error_exit(void)
+  FUNC_ATTR_NORETURN
 {
   if (silent_mode) {  // Normal way to exit for "nvim -es".
     getout(0);

src/nvim/os/signal.c

@@ -152,6 +152,7 @@ static char *signal_name(int signum)
 // NOTE: Avoid unsafe functions, such as allocating memory, they can result in
 // a deadlock.
 static void deadly_signal(int signum)
+  FUNC_ATTR_NORETURN
 {
   // Set the v:dying variable.
   set_vim_var_nr(VV_DYING, 1);

src/nvim/ui_client.c

@@ -87,6 +87,7 @@ Object ui_client_handle_redraw(uint64_t channel_id, Array args, Error *error)
 ///
 /// This is just a stub. the full version will handle input, resizing, etc
 void ui_client_execute(uint64_t chan)
+  FUNC_ATTR_NORETURN
 {
   while (true) {
     loop_poll_events(&main_loop, -1);

src/nvim/window.c

@@ -836,7 +836,7 @@ void ui_ext_win_position(win_T *wp)
   FloatConfig c = wp->w_float_config;
   if (!c.external) {
     ScreenGrid *grid = &default_grid;
-    float row = c.row, col = c.col;
+    Float row = c.row, col = c.col;
     if (c.relative == kFloatRelativeWindow) {
       Error dummy = ERROR_INIT;
       win_T *win = find_window_by_handle(c.window, &dummy);