autotools: add -Wimplicit-fallthrough

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/CODING_STYLE.md b/CODING_STYLE.md
index 80d4096d8d0f56d2617f6430070a906294d5f1ad..54ac6d4ad0ce251b3a4b67fdccabecc18e59696a 100644 (file)
--- a/CODING_STYLE.md
+++ b/CODING_STYLE.md
@@ -633,3 +633,32 @@ string.
 Unless you have a valid reason to accept truncation you must check whether
 truncation has occurred, treat it as an error, and handle the error
 appropriately.
+
+## 25) Use `__fallthrough__` in switch statements
+
+If LXC detects that the compiler is new enough it will tell it to check
+`switch` statements for non-documented fallthroughs. Please always place
+a `__fallthrough__` after a `case` which falls through the next one.
+
+```c
+int lxc_attach_run_command(void *payload)
+{
+       int ret = -1;
+       lxc_attach_command_t *cmd = payload;
+
+       ret = execvp(cmd->program, cmd->argv);
+       if (ret < 0) {
+               switch (errno) {
+               case ENOEXEC:
+                       ret = 126;
+                       break;
+               case ENOENT:
+                       ret = 127;
+                       break;
+               }
+       }
+
+       SYSERROR("Failed to exec \"%s\"", cmd->program);
+       return ret;
+}
+```

diff --git a/config/ax_check_compile_flag.m4 b/config/ax_check_compile_flag.m4
new file mode 100644 (file)
index 0000000..bd753b3
--- /dev/null
+++ b/config/ax_check_compile_flag.m4
@@ -0,0 +1,53 @@
+# ===========================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CHECK_COMPILE_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT])
+#
+# DESCRIPTION
+#
+#   Check whether the given FLAG works with the current language's compiler
+#   or gives an error.  (Warnings, however, are ignored)
+#
+#   ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on
+#   success/failure.
+#
+#   If EXTRA-FLAGS is defined, it is added to the current language's default
+#   flags (e.g. CFLAGS) when the check is done.  The check is thus made with
+#   the flags: "CFLAGS EXTRA-FLAGS FLAG".  This can for example be used to
+#   force the compiler to issue an error when a bad flag is given.
+#
+#   INPUT gives an alternative input source to AC_COMPILE_IFELSE.
+#
+#   NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this
+#   macro in sync with AX_CHECK_{PREPROC,LINK}_FLAG.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
+#   Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.  This file is offered as-is, without any
+#   warranty.
+
+#serial 6
+
+AC_DEFUN([AX_CHECK_COMPILE_FLAG],
+[AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_IF
+AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_[]_AC_LANG_ABBREV[]flags_$4_$1])dnl
+AC_CACHE_CHECK([whether _AC_LANG compiler accepts $1], CACHEVAR, [
+  ax_check_save_flags=$[]_AC_LANG_PREFIX[]FLAGS
+  _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1"
+  AC_COMPILE_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
+    [AS_VAR_SET(CACHEVAR,[yes])],
+    [AS_VAR_SET(CACHEVAR,[no])])
+  _AC_LANG_PREFIX[]FLAGS=$ax_check_save_flags])
+AS_VAR_IF(CACHEVAR,yes,
+  [m4_default([$2], :)],
+  [m4_default([$3], :)])
+AS_VAR_POPDEF([CACHEVAR])dnl
+])dnl AX_CHECK_COMPILE_FLAGS

diff --git a/configure.ac b/configure.ac
index 92d6601d7591804a15e4c2ad4a373ed4f24e5f5b..5428857671031f1ed64ff1c4a3365e478986c8a3 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -683,6 +683,9 @@ AC_PROG_SED
 # See if we support thread-local storage.
 LXC_CHECK_TLS
 
+AX_CHECK_COMPILE_FLAG([-fdiagnostics-color], [CFLAGS="$CFLAGS -fdiagnostics-color"],,[-Werror])
+AX_CHECK_COMPILE_FLAG([-fdiagnostics-color], [CFLAGS="$CFLAGS -Wimplicit-fallthrough"],,[-Werror])
+
 CFLAGS="$CFLAGS -Wvla -std=gnu11"
 if test "x$enable_werror" = "xyes"; then
        CFLAGS="$CFLAGS -Werror"

diff --git a/src/lxc/attach.c b/src/lxc/attach.c
index e109c4640f11fa8096b6b82446630bb875af255e..4c01dea1802b15ac361761a5f566d248e816c46e 100644 (file)
--- a/src/lxc/attach.c
+++ b/src/lxc/attach.c
@@ -1520,8 +1520,10 @@ int lxc_attach_run_command(void *payload)
                switch (errno) {
                case ENOEXEC:
                        ret = 126;
+                       break;
                case ENOENT:
                        ret = 127;
+                       break;
                }
        }
 

diff --git a/src/lxc/cmd/lxc_init.c b/src/lxc/cmd/lxc_init.c
index 362f5b495911c8a0475e63b2513620e0aa0e3b19..388b82173cbc5ac48cad4a4cd5ba5cf33b9a9071 100644 (file)
--- a/src/lxc/cmd/lxc_init.c
+++ b/src/lxc/cmd/lxc_init.c
@@ -39,6 +39,7 @@
 #include <lxc/lxccontainer.h>
 #include <lxc/version.h>
 
+#include "compiler.h"
 #include "error.h"
 #include "initutils.h"
 #include "log.h"
@@ -466,7 +467,7 @@ out:
        exit(exit_with);
 }
 
-static void print_usage(const struct option longopts[])
+__noreturn__ static void print_usage_exit(const struct option longopts[])
 
 {
        fprintf(stderr, "Usage: lxc-init [-n|--name=NAME] [-h|--help] [--usage] [--version]\n\
@@ -474,7 +475,7 @@ static void print_usage(const struct option longopts[])
        exit(0);
 }
 
-static void print_version(void)
+__noreturn__ static void print_version_exit(void)
 {
        printf("%s\n", LXC_VERSION);
        exit(0);
@@ -531,9 +532,9 @@ static int arguments_parse(struct arguments *args, int argc,
                        args->lxcpath = optarg;
                        break;
                case OPT_USAGE:
-                       print_usage(args->options);
+                       print_usage_exit(args->options);
                case OPT_VERSION:
-                       print_version();
+                       print_version_exit();
                case '?':
                        print_help();
                        exit(EXIT_FAILURE);

diff --git a/src/lxc/compiler.h b/src/lxc/compiler.h
index cda44c98790c20721319ff4946fff2f680630b6a..f29ecbed21157144fbe346979d6ae8fbff57c165 100644 (file)
--- a/src/lxc/compiler.h
+++ b/src/lxc/compiler.h
@@ -32,4 +32,18 @@
 #endif
 #endif
 
+#if defined(__GNUC__) && __GNUC__ >= 7 || defined(__clang__)
+#define __fallthrough__ __attribute__((fallthrough))
+#else
+#define __fallthrough__
+#endif
+
+#ifndef _noreturn_
+#if __STDC_VERSION__ >= 201112L
+#define __noreturn__ _Noreturn
+#else
+#define __noreturn__ __attribute__((noreturn))
+#endif
+#endif
+
 #endif /* __LXC_COMPILER_H */

diff --git a/src/lxc/tools/arguments.c b/src/lxc/tools/arguments.c
index f6ee123dce813b12c58ba14ad820baa9202dfc09..e1e4c6e4975e1ceabebb7ad856266269e9edf8a6 100644 (file)
--- a/src/lxc/tools/arguments.c
+++ b/src/lxc/tools/arguments.c
@@ -37,6 +37,7 @@
 #include <lxc/version.h>
 
 #include "arguments.h"
+#include "compiler.h"
 #include "namespace.h"
 #include "initutils.h"
 
@@ -87,8 +88,8 @@ is2big:
        return -1;
 }
 
-static void print_usage_exit(const struct option longopts[],
-                            const struct lxc_arguments *a_args)
+__noreturn__ static void print_usage_exit(const struct option longopts[],
+                                         const struct lxc_arguments *a_args)
 
 {
        int i;
@@ -134,13 +135,14 @@ static void print_usage_exit(const struct option longopts[],
        exit(0);
 }
 
-static void print_version_exit()
+__noreturn__ static void print_version_exit()
 {
        printf("%s\n", lxc_get_version());
        exit(0);
 }
 
-static void print_help_exit(const struct lxc_arguments *args, int code)
+__noreturn__ static void print_help_exit(const struct lxc_arguments *args,
+                                        int code)
 {
        fprintf(stderr, "\
 Usage: %s %s\