Bug#53445: Build with -Wall and fix warnings that it generates

Introduce a MySQL maintainer/developer mode that enables
a set of warning options for the C/C++ compiler. This mode
is intended to help improve the overall quality of the code.

The warning options are:

C_WARNINGS="-Wall -Wextra -Wunused -Wwrite-strings -Werror"
CXX_WARNINGS="$C_WARNINGS -Wno-unused-parameter"

Since -Wall is essentially a moving target, autoconf checks
are not run with warning options enabled, in particualr -Werror.
This decision might be revisited in the future. The patch also
fixes a mistake in the makefiles, where automake CXXFLAGS would
be set to CFLAGS.

config/ac-macros/maintainer.m4:
  Add a set of default compiler flags used when in maintainer mode.
configure.in:
  Hook into the maintainer mode. Disabled by default.

1 files changed, 66 insertions, 0 deletions

diff --git a/config/ac-macros/maintainer.m4 b/config/ac-macros/maintainer.m4
new file mode 100644
index 00000000000..6aa1d166f2a
--- /dev/null
+++ b/config/ac-macros/maintainer.m4
@@ -0,0 +1,66 @@
+#
+# Control aspects of the development environment which are
+# specific to MySQL maintainers and developers.
+#
+AC_DEFUN([MY_MAINTAINER_MODE], [
+  AC_MSG_CHECKING([whether to enable the maintainer-specific development environment])
+  AC_ARG_ENABLE([mysql-maintainer-mode],
+    [AS_HELP_STRING([--enable-mysql-maintainer-mode],
+                    [Enable a MySQL maintainer-specific development environment])],
+    [USE_MYSQL_MAINTAINER_MODE=$enableval],
+    [USE_MYSQL_MAINTAINER_MODE=no])
+  AC_MSG_RESULT([$USE_MYSQL_MAINTAINER_MODE])
+])
+
+# Set warning options required under maintainer mode.
+AC_DEFUN([MY_MAINTAINER_MODE_WARNINGS], [
+  # Setup GCC warning options.
+  AS_IF([test "$GCC" = "yes"], [
+    C_WARNINGS="-Wall -Wextra -Wunused -Wwrite-strings -Werror"
+    CXX_WARNINGS="${C_WARNINGS} -Wno-unused-parameter"
+  ])
+
+  # Test whether the warning options work.
+  # Test C options
+  AS_IF([test -n "$C_WARNINGS"], [
+    save_CFLAGS="$CFLAGS"
+    AC_MSG_CHECKING([whether to use C warning options ${C_WARNINGS}])
+    AC_LANG_PUSH(C)
+    CFLAGS="$CFLAGS ${C_WARNINGS}"
+    AC_LANG_WERROR
+    AC_COMPILE_IFELSE([AC_LANG_PROGRAM()], [myac_c_warning_flags=yes],
+                      [myac_c_warning_flags=no])
+    AC_LANG_POP()
+    AC_MSG_RESULT([$myac_c_warning_flags])
+    CFLAGS="$save_CFLAGS"
+  ])
+
+  # Test C++ options
+  AS_IF([test -n "$CXX_WARNINGS"], [
+    save_CXXFLAGS="$CXXFLAGS"
+    AC_MSG_CHECKING([whether to use C++ warning options ${CXX_WARNINGS}])
+    AC_LANG_PUSH(C++)
+    CXXFLAGS="$CXXFLAGS ${CXX_WARNINGS}"
+    AC_LANG_WERROR
+    AC_COMPILE_IFELSE([AC_LANG_PROGRAM()], [myac_cxx_warning_flags=yes],
+                      [myac_cxx_warning_flags=no])
+    AC_LANG_POP()
+    AC_MSG_RESULT([$myac_cxx_warning_flags])
+    CXXFLAGS="$save_CXXFLAGS"
+  ])
+
+  # Set compile flag variables.
+  AS_IF([test "$myac_c_warning_flags" = "yes"], [
+    AM_CFLAGS="${AM_CFLAGS} ${C_WARNINGS}"
+    AC_SUBST([AM_CFLAGS])])
+  AS_IF([test "$myac_cxx_warning_flags" = "yes"], [
+    AM_CXXFLAGS="${AM_CXXFLAGS} ${CXX_WARNINGS}"
+    AC_SUBST([AM_CXXFLAGS])])
+])
+
+
+# Set compiler flags required under maintainer mode.
+AC_DEFUN([MY_MAINTAINER_MODE_SETUP], [
+  AS_IF([test "$USE_MYSQL_MAINTAINER_MODE" = "yes"],
+        [MY_MAINTAINER_MODE_WARNINGS])
+])