[Bug c/80892] New: [8 regression] -Wfloat-conversion now warns about non-floats

[egall at gwmail dot gwu.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80892

            Bug ID: 80892
           Summary: [8 regression] -Wfloat-conversion now warns about
                    non-floats
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: egall at gwmail dot gwu.edu
                CC: msebor at gcc dot gnu.org
  Target Milestone: ---
              Host: i386-apple-darwin10.8.0
            Target: i386-apple-darwin10.8.0
             Build: i386-apple-darwin10.8.0

Previously, it was possible to request warnings about just conversions
involving floating point types by specifying -Wfloat-conversion. However, with
my latest build from trunk, -Wfloat-conversion seems to have become an alias
for -Wconversion, meaning that it now warns on things like:

/usr/local/bin/gcc -c -DHAVE_CONFIG_H -g -O2 -arch i386  -I. -I./../include
-D_DARWIN_UNLIMITED_STREAMS -mmacosx-version-min=10.5 -Wall -Wextra
-Wwrite-strings -Wc++-compat -Wodr -Wstrict-prototypes -Wmissing-prototypes
-Wmissing-parameter-type -Wmissing-declarations -Wnested-externs -Wundef
-Wshadow -Wformat=2 -Wformat-overflow=2 -Wformat-truncation=2
-Wstringop-overflow=2 -Walloc-zero -Wrestrict -Wold-style-definition
-Wold-style-declaration -Wfloat-conversion -Wabi -Wc99-c11-compat
-Wmisleading-indentation -Wnull-dereference -Wpointer-compare -Wbool-operation
-pedantic  ./cp-demangle.c -o cp-demangle.o
./cp-demangle.c: In function 'd_print_java_identifier':
./cp-demangle.c:3473:27: warning: conversion from 'long unsigned int' to 'char'
may change value [-Wfloat-conversion]
        d_append_char(dpi, c);
                           ^

This means I now have a bunch of new warnings in my build where I previously
didn't, because I'm only using -Wfloat-conversion and not the full
-Wconversion. cc-ing Martin Sebor since he was the last one I remember seeing
posting patches touching the -Wconversion code.

gcc version info:
$ /usr/local/bin/gcc -v
Using built-in specs.
COLLECT_GCC=/usr/local/bin/gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/i386-apple-darwin10.8.0/8.0.0/lto-wrapper
Target: i386-apple-darwin10.8.0
Configured with: ../configure --disable-werror --disable-werror-always
--enable-languages=c,c++,objc,obj-c++,lto --enable-stage1-checking=release,rtl
-C --with-system-libunwind --enable-secureplt --enable-frame-pointer
--enable-debug --without-isl --disable-host-shared --enable-maintainer-mode
--disable-default-pie --with-ld64 --without-pic --enable-target-optspace
--disable-nls --with-system-zlib --with-libiconv-prefix=/opt/local
--with-gmp=/opt/local --with-mpfr=/opt/local --with-mpc=/opt/local --enable-lto
--enable-libstcxx-time --with-build-config=bootstrap-debug
--with-as=/opt/local/bin/as --with-ld=/opt/local/bin/ld
--with-ar=/opt/local/bin/ar --enable-objc-gc --enable-libada --enable-libssp
CC='/usr/bin/gcc-4.2 -arch i386 -arch x86_64' CXX='/usr/bin/g++-4.2 -arch
x86_64' AR_FOR_TARGET=/opt/local/bin/ar AS_FOR_TARGET=/opt/local/bin/as
LD_FOR_TARGET=/opt/local/bin/ld NM_FOR_TARGET=/opt/local/bin/nm
RANLIB_FOR_TARGET=/opt/local/bin/ranlib STRIP_FOR_TARGET=/opt/local/bin/strip
OTOOL=/opt/local/bin/otool OTOOL64=/opt/local/bin/otool
AUTOCONF=/opt/local/bin/autoconf264 AUTOHEADER=/opt/local/bin/autoheader264
AUTOM4TE=/opt/local/bin/autom4te264 AUTORECONF=/opt/local/bin/autoreconf264
AUTOSCAN=/opt/local/bin/autoscan264 AUTOUPDATE=/opt/local/bin/autoupdate264
IFNAMES=/opt/local/bin/ifnames264 ACLOCAL=/sw/bin/aclocal-1.11
PERL=/opt/local/bin/perl CFLAGS='-pipe -g -Os' CXXFLAGS='-pipe -g -Os
-fcheck-new' CPP='/usr/bin/gcc-4.2 -E' CXXCPP='/usr/bin/g++-4.2 -E'
M4=/opt/local/bin/gm4
Thread model: posix
gcc version 8.0.0 20170525 (experimental) (GCC)