error C2220: warning treated as error, warning C4702: unreachable code

[jptrainor]

On Windows, the boost::locale test_std_convert.cpp test will fail to compile due to an unreachable code warning:

 ...\boost_1_82_0\libs\locale\test\test_std_formatting.c
 pp(152) : error C2220: warning treated as error - no 'object' file generated
 ...\boost_1_82_0\libs\locale\test\test_std_formatting.c
 pp(152) : warning C4702: unreachable code

Test Platform:

• Windows 10 version 22H2
• Windows Python, for the ICI build
• Visual Studio 2017 Community Edition version 15.9.55
• ICU 71.1
• Boost 1.82.0
• boost.locale.icu=on boost.locale.winapi=on

Compiling the boost::locale tests with cxxflags="\wd4702" works around the problem.

Here is a Cygwin bash script that downloads icu and boost, compiles both, and will as with the unreachable code warning noted above.

#! /bin/bash -x

# Download icu and boost, build icu, build boost --with-locale, and 
# build the boost::locale tests.
#
# The boost::locale test_std_formatting.cpp file, and other test files, will fail to
# compile due to an unreachable code warning:
#
# ...\boost_1_82_0\libs\locale\test\test_std_formatting.c
# pp(152) : error C2220: warning treated as error - no 'object' file generated
# ...\boost_1_82_0\libs\locale\test\test_std_formatting.c
# pp(152) : warning C4702: unreachable code
#
# Compiling the boost::locale tests with cxxflags="\wd4702" works around the
# problem by disabling the unreachable code warning.
#
# Test Platform:
#   Windows 10 version 22H2
#   Visual Studio 2017 Community Edition version 15.9.55
#   Cygwin to run this script

set -e

# Windows path to local Visual Studio environment setup batch file.
WIN_VCVARSALL_BAT="c:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvarsx86_amd64.bat"

# Don't raise ICU version beyond 71.1 until
# https://github.com/boostorg/locale/issues/176 is resolved.
ICU_VER="71.1"
ICU_RELEASE=release-$(echo $ICU_VER | sed s/\\./-/)
ICU4C_SRC=icu4c-$(echo $ICU_VER | sed s/\\./_/)-src

BOOST_VER="1.82.0"
BOOST_SRC=boost_$(echo $BOOST_VER | sed s/\\./_/g)

# setup error trap
function ErrorTrap {
    echo FAILED
}
trap ErrorTrap INT TERM EXIT

DIR=boost_locale_windows_unreachable_warning.$(date "+%m-%d-%y_%H-%M-%S").d
mkdir $DIR
cd $DIR

# setup log
exec > >(tee boost_locale_windows_unreachable_warning.log)
exec 2> >(tee -a boost_locale_windows_unreachable_warning.log)

# Run windows build command by writing a temporary windows bat file
# and executing it using cmd.exe.  The visual studio environment is
# configured (vcvarsall.bat) before the build command.
function wincmd {
    local cmd="$*"
    local batfile=$(mktemp wincmd_tmp_XXXXXX.bat)

    cat <<__EOF > "$batfile"
call "$WIN_VCVARSALL_BAT"
$cmd
__EOF

    cat $batfile

    cmd.exe /c "$batfile"
}

# get icu
wget --quiet --no-check-certificate "https://github.com/unicode-org/icu/releases/download/${ICU_RELEASE}/${ICU4C_SRC}.tgz"
tar xvzf "${ICU4C_SRC}".tgz
ICU_PATH=${PWD}/icu

# get boost
wget --quiet --no-check-certificate "https://boostorg.jfrog.io/artifactory/main/release/"${BOOST_VER}"/source/"${BOOST_SRC}".tar.gz"
tar xvzf "${BOOST_SRC}".tar.gz

(
    cd icu/source
    wincmd msbuild allinone\\allinone.sln /p:Configuration=Debug /p:Platform=x64
    wincmd msbuild allinone\\allinone.sln /p:Configuration=Debug /p:Platform=x64 /target:makedata
)

(
    cd ${BOOST_SRC}

    wincmd bootstrap.bat

    wincmd b2 debug -j4 \
          -sICU_PATH=$(cygpath -w "${ICU_PATH}") \
          boost.locale.icu=on boost.locale.iconv=off boost.locale.winapi=on boost.locale.std=off boost.locale.posix=off \
          --with-locale \
          toolset="msvc-14.1" \
          architecture=x86 \
          address-model=64

    # This fails with "error C2220: warning treated as error" do to
    # "warning C4702: unreachable code" when compiling
    # test_std_formatting.cpp. Compiling with cxxflags="\wd4702" works
    # around the problem.
    unset TZ;
    wincmd b2 debug -j4 \
          -sICU_PATH=$(cygpath -w "${ICU_PATH}") \
          boost.locale.icu=on boost.locale.iconv=off boost.locale.winapi=on boost.locale.std=off boost.locale.posix=off \
          --with-locale \
          toolset="msvc-14.1" \
          architecture=x86 \
          address-model=64 \
          libs/locale/test
)

# clear error trap
trap - INT TERM EXIT

echo PASSED

[Flamefire]

Thanks for the report, looks like we don't test with disabled std backend which although possible might not be so useful in practice and hence wasn't included in CI.

Will be fixed.