From 71a8648145861cebde04cebf4de8ce10e21b7904 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tim Rühsen?= <address@hidden>
Date: Sun, 18 Jun 2017 12:33:08 +0200
Subject: [PATCH] Add m4/wget_manywarnings

This enables (if switched on) basically all warnings for gcc and clang.
Exceptions are explicitly controlled in configure.ac.

To enable by default: create a file '.manywarnings'
Enable explicitly : ./configure --enable-manywarnings
Disable explicitly: ./configure --disable-manywarnings

New warnings of new compiler versions are automatically added.
This module works much faster than the 'manywarnings' module from gnulib.

Created for developers and Continuous Integration.
---
 configure.ac               | 53 ++++++++++++++++++++++++++++
 m4/wget_manywarnings.m4    | 88 ++++++++++++++++++++++++++++++++++++++++++++++
 src/microhttpd/Makefile.am |  2 +-
 3 files changed, 142 insertions(+), 1 deletion(-)
 create mode 100644 m4/wget_manywarnings.m4

diff --git a/configure.ac b/configure.ac
index 443dcf24..b4b28748 100644
--- a/configure.ac
+++ b/configure.ac
@@ -338,6 +338,59 @@ netbsd*)
 ;;
 esac

+
+# enable all possible compiler warnings in WARN_FLAGS
+#
+# to enable by default: create a file '.manywarnings'
+# enable explicitly : ./configure --enable-manywarnings
+# disable explicitly: ./configure --disable-manywarnings
+wget_MANYWARNINGS(WARN_CFLAGS, C)
+
+if test -n "$WARN_CFLAGS"; then
+  if test "$CCNAME" = "gcc"; then
+    # Set up list of unwanted warnings
+    nw+    nw="$nw -Wsystem-headers"       # System headers may trigger lot's of useless warnings
+    nw="$nw -Wvla"                  # This project is C99
+    nw="$nw -Wstack-protector"
+    nw="$nw -Wmissing-field-initializer"
+    nw="$nw -Wtraditional"
+    nw="$nw -Wtraditional-conversion"
+    nw="$nw -Wc++-compat"
+    nw="$nw -Wcast-qual"
+    nw="$nw -Wconversion"
+    nw="$nw -Wsign-conversion"
+    nw="$nw -Wunsuffixed-float-constants"
+    nw="$nw -Wdeclaration-after-statement" # C89 only, messing up gcc < 5
+    if test "$cross_compiling" = yes; then
+      nw="$nw -Wformat"
+    fi
+
+    # remove unwanted warn flags
+    wget_WORD_REMOVE([WARN_CFLAGS], [$WARN_CFLAGS], [$nw])
+
+    # add more flags as you like
+    WARN_CFLAGS="$WARN_CFLAGS -fdiagnostics-color=always"
+    if test "$cross_compiling" = yes; then
+      WARN_CFLAGS="$WARN_CFLAGS -Wno-format"
+    fi
+    # WARN_CFLAGS="$WARN_CFLAGS -Werror"
+
+  elif test "$CCNAME" = "clang"; then
+    # setup flags for this project
+    WARN_CFLAGS="$WARN_CFLAGS -Wno-system-headers -Wno-vla -Wno-cast-qual -Wno-padded"
+    WARN_CFLAGS="$WARN_CFLAGS -Wno-reserved-id-macro -Wno-sign-conversion  -Wno-disabled-macro-expansion"
+    WARN_CFLAGS="$WARN_CFLAGS -Wno-documentation -Wno-documentation-unknown-command"
+    WARN_CFLAGS="$WARN_CFLAGS -Wno-covered-switch-default"
+
+    # remove all flags from WARN_FLAGS that are already in CFLAGS
+    # wget_WORD_REMOVE([WARN_CFLAGS], [$WARN_CFLAGS], [$CFLAGS])
+ fi
+
+  AC_SUBST([WARN_CFLAGS])
+fi
+
+
 AC_ARG_WITH([threads],
    [AS_HELP_STRING([--with-threads=LIB],[choose threading library (posix, w32, auto) [auto]])],
    [], [with_threads='auto'])
diff --git a/m4/wget_manywarnings.m4 b/m4/wget_manywarnings.m4
new file mode 100644
index 00000000..61033282
--- /dev/null
+++ b/m4/wget_manywarnings.m4
@@ -0,0 +1,88 @@
+# wget_manywarnings.m4 serial 1
+dnl Copyright (C) 2016 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Tim Ruehsen
+
+# wget_WORD_SET(RESULT, SET, WORDS)
+# --------------------------------------------------
+# Add each word in WORDS to SET if not already there and store in RESULT.
+# Words separated by whitespace.
+AC_DEFUN([wget_WORD_SET], [
+  ret=$2
+  words=" $2 "
+  for word in $3; do
+    if test "${words#*" $word "}" = "$words"; then ret="$ret $word"; fi
+  done
+  $1=$ret
+])
+
+# wget_WORD_REMOVE(RESULT, SET, WORDS)
+# --------------------------------------------------
+# Remove each word in WORDS from SET and store in RESULT.
+# Words separated by whitespace.
+AC_DEFUN([wget_WORD_REMOVE], [
+  ret+  words=" $3 "
+  for word in $2; do
+     if test "${words#*" $word "}" = "$words"; then ret="$ret $word"; fi
+  done
+  $1=$ret
+])
+
+# wget_MANYWARNINGS(VARIABLE, LANGUAGE)
+# -----------------------------
+# Add LANGUAGE related GCC warnings to VARIABLE.
+# This only works for gcc >= 4.3.
+AC_DEFUN([wget_MANYWARNINGS], [
+  #
+  # check if manywarnings is requested
+  #
+  AC_ARG_ENABLE([manywarnings],
+    [AS_HELP_STRING([--enable-manywarnings], [Turn on extra compiler warnings (for developers)])],
+    [case $enableval in
+       yes|no) ;;
+       *) AC_MSG_ERROR([Bad value $enableval for --enable-manywarnings option]) ;;
+     esac
+       wget_manywarnings=$enableval
+    ], [
+      test -f .manywarnings && wget_manywarnings=yes || wget_manywarnings=no
+    ]
+  )
+
+  $1=""
+
+  if test "$wget_manywarnings" = yes; then
+    # AC_PROG_CC sets $GCC to 'yes' if compiler is gcc
+    # AC_REQUIRE([AC_PROG_CC])
+
+    case $CC in
+      *gcc*) CCNAME="gcc";;
+      *clang*) CCNAME="clang";;
+    esac
+
+    if test "$CCNAME" = "gcc"; then
+      test -n "$2" && wget_LANGUAGE=$2 || wget_LANGUAGE=C
+
+      # add -Wall -Wextra to reduce number of warn flags
+      wget_WORD_SET([wget_WARN_CFLAGS], [$CFLAGS], ["-Wall -Wextra -Wformat=2"])
+
+      # collect all disabled warn flags in $WARN_CFLAGS
+      wget_WARN_CFLAGS=$wget_WARN_CFLAGS" "$($CC $wget_WARN_CFLAGS -Q --help=warning,$wget_LANGUAGE|\
+        awk '{ if (([$]2 == "[[disabled]]" || [$]2 == "") && [$]1!~/=/ && [$]1~/^-W/&& [$]1!="-Wall") print [$]1 }')
+
+      GCC_VERSION=$($CC -dumpversion | cut -f1 -d.)
+      if test $GCC_VERSION -ge 6; then
+        wget_WARN_CFLAGS=$wget_WARN_CFLAGS" -Warray-bounds=2 -Wnormalized=nfc -Wshift-overflow=2 -Wunused-const-variable=2"
+      fi
+
+    elif test "$CCNAME" = "clang"; then
+      # set all warn flags on
+      wget_WORD_SET([wget_WARN_CFLAGS], [$CFLAGS], ["-Weverything"])
+    fi
+
+    $1=$wget_WARN_CFLAGS
+  fi
+])
diff --git a/src/microhttpd/Makefile.am b/src/microhttpd/Makefile.am
index 5ae900ac..b35d0482 100644
--- a/src/microhttpd/Makefile.am
+++ b/src/microhttpd/Makefile.am
@@ -3,7 +3,7 @@ AM_CPPFLAGS = \
   -I$(top_srcdir)/src/include \
   -I$(top_srcdir)/src/microhttpd

-AM_CFLAGS = $(HIDDEN_VISIBILITY_CFLAGS)
+AM_CFLAGS = $(HIDDEN_VISIBILITY_CFLAGS) $(WARN_CFLAGS)

 lib_LTLIBRARIES = \
   libmicrohttpd.la
--
2.11.0