Description:
------------
/usr/src/php/ext/sockets/multicast.c: In function 'php_add4_to_if_index':
/usr/src/php/ext/sockets/multicast.c:793:6: warning: comparison of distinct pointer types lacks a cast
    p < if_conf.ifc_buf + if_conf.ifc_len;
      ^

Test script:
---------------
FROM php:7.1-fpm-alpine AS build-env
RUN docker-php-source extract
RUN echo '@edge-main http://dl-cdn.alpinelinux.org/alpine/edge/main' >> /etc/apk/repositories
RUN echo '@edge-community http://dl-cdn.alpinelinux.org/alpine/edge/community' >> /etc/apk/repositories
RUN echo '@edge-testing http://dl-cdn.alpinelinux.org/alpine/edge/testing' >> /etc/apk/repositories
RUN apk update
RUN apk add --upgrade apk-tools@edge-main

RUN apk add \
    coreutils \
    postgresql-dev@edge-main \
    libmcrypt-dev \
    bzip2-dev \
    libpng-dev \
    libxslt-dev \
    gettext-dev \
    autoconf \
    g++ \
    make \
    cmake \
    geoip-dev \
    libmemcached-dev \
    cyrus-sasl-dev \
    pcre-dev \
    git \
    file \
    freetype-dev \
    libjpeg-turbo-dev \
    re2c \
    libressl-dev@edge-main \
    rabbitmq-c-dev@edge-main

RUN docker-php-ext-configure \
    gd --with-freetype-dir=/usr/lib --with-jpeg-dir=/usr/lib --with-png-dir=/usr/lib

RUN docker-php-ext-install -j$(getconf _NPROCESSORS_ONLN) \
    mcrypt \
    mysqli \
    bz2 \
    opcache \
    calendar \
    gd \
    pcntl \
    xsl \
    soap \
    shmop \
    sysvmsg \
    sysvsem \
    sysvshm \
    sockets \
    pdo_mysql \
    pdo_pgsql \
    pgsql \
    wddx


Expected result:
----------------
No warning message in the build log.

Actual result:
--------------
/usr/src/php/ext/sockets/multicast.c: In function 'php_add4_to_if_index':
/usr/src/php/ext/sockets/multicast.c:793:6: warning: comparison of distinct pointer types lacks a cast
    p < if_conf.ifc_buf + if_conf.ifc_len;
      ^