How to build libiconv with VC2017

最近解決了VC2017編譯libiconv的問題，總結一下經驗和收穫。
按照GNU libiconv官方的README.windows文檔“2) Native binaries, built using the MS Visual C/C++ tool chain.”的說明，應該是在Cygwin環境下使用Visual C/C++ 9.0或以上版本進行。
網上介紹VC編譯libiconv的文章很多，採用官方推薦做法的卻很少，奇哉怪也！我在解決的過程中發現原來這個過程有好幾個坑，可能是因爲這個原因吧。

1. fprintf()輸出’\n’換行符問題

libiconv/lib/genaliases.c輸出’\n’到以文本方式打開的canonical.sh，這導致在Cygwin中生成的Unix腳本文件用的換行符卻是DOS格式，然後導致腳本中的sed程序處理出錯。
這個問題已在官方代碼庫修正（在libiconv-1.15之後），改爲以二進制方式打開文件。

參考

[1] Avoid end-of-lines problem in generated shell scripts on Cygwin.
[2] Text and Binary modes

2. windres的-F參數問題

在libiconv/lib/Makefile.in中:

libiconv.res.lo : $(srcdir)/../windows/libiconv.rc
    $(LIBTOOL_COMPILE) --tag=RC $(RC) `$(SHELL) $(srcdir)/../windows/windres-options --escape $(PACKAGE_VERSION)` -i $(srcdir)/../windows/libiconv.rc -o libiconv.res.lo --output-format=coff

在libiconv/src/Makefile.in中:

iconv.res : $(srcdir)/../windows/iconv.rc
    $(WINDRES) `$(SHELL) $(srcdir)/../windows/windres-options --escape $(PACKAGE_VERSION)` -i $(srcdir)/../windows/iconv.rc -o iconv.res --output-format=coff

這裏$(RC)和$(WINDRES)在生成的Makefile中就對應了Cygwin的windres程序。（不能用Windows平臺的rc.exe，因爲它不支持output-format參數）。
libiconv的出現遠早於64位Windows。在64位Windows的Cygwin64終端上，windres默認將rc資源文件編譯成64位的res文件。如果要編譯的是32位的libiconv，link鏈接時就出錯了。
解決辦法是在”configure”的運行參數中增加

    RC="windres -Fpe-i386" WINDRES="windres -Fpe-i386"

如果是64位的目標，則增加：

    RC="windres -Fpe-x86-64" WINDRES="windres -Fpe-x86-64"

鏈接器link也有類似問題，需要在LDFLAGS中添加“/MACHINE:X86”或“/MACHINE:X64”。
這個問題只能建議官方更新README.windows文檔了。

參考

[1] windres

3. UTF-8字符導致C4819編譯警告的問題

先看這個補丁：Use Unicode single-quotes in comments.
對於Windows系統區域和語言設置不是英語的用戶，代碼中的UTF-8字符會導致MSVC報告C4819編譯警告。
關鍵問題是編譯器不能正確處理後續代碼了，後面經常就跟着報編譯錯誤，然後是編譯失敗和鏈接失敗。
關於這個問題網上也有很多解決方案：

a. 修改Windows區域和語言設置

改成英語國家，就是日常使用不太方便了。可能美國同行都沒注意到有UTF-8導致C4819這回事。

b. 轉碼後保存

網上很多介紹怎麼通過VC界面手動保存的，不抄了。我自己寫的bash版：

    if [ ! `regtool -q check/HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Control/Nls/CodePage/OEMCP` ]; then
        TOCODEPAGE=`regtoolget /HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Control/Nls/CodePage/OEMCP`
        cp include/iconv.h include/iconv.h.backup
        iconv-c -f utf-8 -t cp"${TOCODEPAGE}" include/iconv.h 1>include/iconv.h.tmp
        mv include/iconv.h.tmp include/iconv.h
        make
        make check
        make install
        mv include/iconv.h.backup include/iconv.h
    fi

之前爲另一項目做的DOS批處理文件版：

FOR %%X IN (src\*.*, include\artilist.h, dat\*.*, win\win32\*.c) DO (
    iconv.exe -c -f utf-8 -t gb18030 %%X 1> %%X.gb
    mv.exe %%X.gb %%X
)

c. 不修改代碼

給CFLAGS和CXXFLAGS加”/utf-8”參數，詳見下面的參考[1]。

d. 不要在C/C++代碼裏用UTF-8

把前面提到的補丁取消掉是最好的，畢竟iconv.h還要導出給庫用戶使用的，不改的話就是把問題推給用戶了。
C/C++源文件最好只用ASCII字符編碼。有多語言需求的可以放到程序外去實現，比如配置文件、數據庫或其他明確支持UTF-8的腳本語言。

參考

[1] /utf-8 (Set Source and Executable character sets to UTF-8)
[2] Unicode Support in the Compiler and Linker
[3] Compile error with source file containing UTF8 strings (in CJK system locale)
[4] It is impossible to use UTF-8 without BOM in source files.

4. build-vc2017.sh

我寫的輔助腳本，僅供參考。

#!/bin/sh
if [ ! -f configure ]; then
    echo Install Cygwin packages: autoconf make automake gcc-core gettext-devel git gperf groff m4 patch
    echo Then run ./autogen.sh before this script.
    exit 1
fi

# Set PlatformTarget
# Remember to "make clean" after switching PlatformTarget, before running this script again.
#PlatformTarget=x64
if [ -z "${PlatformTarget}" ]; then
    PlatformTarget=x86
fi

# Get WindowsSdkDir
#WindowsSdkDir='C:\\Program Files (x86)\\Windows Kits\\10\\'
if [ -z "${WindowsSdkDir}" ]; then
    REGISTRY1=/HKEY_LOCAL_MACHINE/SOFTWARE/Wow6432Node/Microsoft/Microsoft\ SDKs/Windows/v10.0
    REGISTRY2=/HKEY_CURRENT_USER/SOFTWARE/Wow6432Node/Microsoft/Microsoft\ SDKs/Windows/v10.0
    REGISTRY3=/HKEY_LOCAL_MACHINE/SOFTWARE/Microsoft/Microsoft\ SDKs/Windows/v10.0
    REGISTRY4=/HKEY_CURRENT_USER/SOFTWARE/Microsoft/Microsoft\ SDKs/Windows/v10.0
    if [ ! `regtool -q check "${REGISTRY1}/InstallationFolder"` ]; then
        WindowsSdkDir=`regtool get "${REGISTRY1}/InstallationFolder"`
    elif [ ! `regtool -q check "$REGISTRY2/InstallationFolder"` ]; then
        WindowsSdkDir=`regtool get "${REGISTRY2}/InstallationFolder"`
    elif [ ! `regtool -q check "$REGISTRY3/InstallationFolder"` ]; then
        WindowsSdkDir=`regtool get "${REGISTRY3}/InstallationFolder"`
    elif [ ! `regtool -q check "$REGISTRY4/InstallationFolder"` ]; then
        WindowsSdkDir=`regtool get "${REGISTRY4}/InstallationFolder"`
    else
        echo Cannot find WindowsSdkDir
        exit 1;
    fi
fi

if [ ! -d "${WindowsSdkDir}" ]; then
    echo Cannot find WindowsSdkDir ${WindowsSdkDir}
    exit 1
fi

# Set WindowsSDKVersion
#WindowsSDKVersion='10.0.15063.0'
#WindowsSDKVersion='10.0.14393.0'
#WindowsSDKVersion='10.0.10586.0'
#WindowsSDKVersion='10.0.10240.0'
if [ -z "${WindowsSDKVersion}" ]; then
    WindowsSDKVersion='10.0.16299.0'
fi

# Set VSINSTALLDIR
VSINSTALLDIR='D:\Program Files (x86)\Microsoft Visual Studio\2017\Community\'
#VSINSTALLDIR='E:\Program Files (x86)\Microsoft Visual Studio\2017\Community\'
#VSINSTALLDIR='F:\Program Files (x86)\Microsoft Visual Studio\2017\Community\'
#VSINSTALLDIR='G:\Program Files (x86)\Microsoft Visual Studio\2017\Community\'
if [ -z "${VSINSTALLDIR}" ]; then
    VSINSTALLDIR='C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\'
fi

# Set VSToolsVersion
#VSToolsVersion='14.11.25503'
if [ -z "${VSToolsVersion}" ]; then
    VSToolsVersion='14.11.25503'
fi

echo PlatformTarget=${PlatformTarget}
echo WindowsSdkDir=${WindowsSdkDir}
echo WindowsSDKVersion=${WindowsSDKVersion}
echo VSINSTALLDIR=${VSINSTALLDIR}
echo VSToolsVersion=${VSToolsVersion}
echo

# Verify WindowsSdkIncludeDir and WindowsSdkLibDir
WindowsSdkIncludeDir="${WindowsSdkDir}"'Include\'"${WindowsSDKVersion}"
WindowsSdkLibDir="${WindowsSdkDir}"'Lib\'"${WindowsSDKVersion}"
if [ ! -d "${WindowsSdkIncludeDir}" ]; then
        echo Cannot find WindowsSdkIncludeDir ${WindowsSdkIncludeDir}
    echo Modify WindowsSDKVersion value and run again.
    exit 1
fi
if [ ! -d "${WindowsSdkLibDir}" ]; then
        echo Cannot find WindowsSdkLibDir ${WindowsSdkLibDir}
    echo Modify WindowsSDKVersion value and run again.
    exit 1
fi

# Windows C library headers and libraries.
WindowsCrtIncludeDir="${WindowsSdkIncludeDir}\\ucrt"
WindowsCrtLibDir="${WindowsSdkLibDir}"'\ucrt\'"${PlatformTarget}"
if [ ! -f "${WindowsCrtIncludeDir}\\stdio.h" ]; then 
    echo Cannot locate ${WindowsCrtIncludeDir}\\stdio.h
    exit 1
fi
if [ ! -f "${WindowsCrtLibDir}\\ucrt.lib" ]; then
    echo Cannot locate ${WindowsCrtLibDir}\\ucrt.lib
    exit 1
fi
INCLUDE="${WindowsCrtIncludeDir};$INCLUDE"
LIB="${WindowsCrtLibDir};$LIB"

# Windows API headers and libraries.
INCLUDE="${WindowsSdkIncludeDir}\\um;${WindowsSdkIncludeDir}\\shared;$INCLUDE"
LIB="${WindowsSdkLibDir}"'\um\'"${PlatformTarget};$LIB"

# Visual C++ tools, headers and libraries.
VCToolsInstallDir="${VSINSTALLDIR}"'VC\Tools\MSVC\'"${VSToolsVersion}"
if [ ! -f "${VCToolsInstallDir}\\include\\stdarg.h" ]; then
        echo Cannot locate ${VCToolsInstallDir}\\include\\stdarg.h
    echo Modify VSINSTALLDIR and VSToolsVersion values and run again.
    exit 1
fi
INCLUDE="${VCToolsInstallDir}\\include;$INCLUDE"
LIB="${VCToolsInstallDir}"'\lib\'"${PlatformTarget};$LIB"

export INCLUDE LIB
#echo INCLUDE=${INCLUDE}
#echo LIB=${LIB}
#echo
#read -n1 -p "Verify the above settings. Press CTRL-C to abort, or other keys to continue..."

[ -d $HOME/msvc/ ] || mkdir $HOME/msvc/
cp gnulib/build-aux/ar-lib $HOME/msvc/ && chmod a+x $HOME/msvc/ar-lib
cp gnulib/build-aux/compile $HOME/msvc/ && chmod a+x $HOME/msvc/compile

if [ "${PlatformTarget}" == "x86" ]; then
    export PATH=`cygpath -u "${VCToolsInstallDir}"`/bin/Hostx86/x86:`cygpath -u "${WindowsSdkDir}"`bin/"${WindowsSDKVersion}"/x86:"$PATH"
    win32_target=_WIN32_WINNT_WIN7
    ./configure --host=i686-w64-mingw32 --prefix=/usr/local/msvc32 \
        CC="$HOME/msvc/compile cl -nologo" \
        CFLAGS="-MD /utf-8" \
        CXX="$HOME/msvc/compile cl -nologo" \
        CXXFLAGS="-MD /utf-8" \
        CPPFLAGS="-D_WIN32_WINNT=$win32_target" \
        RC="windres -Fpe-i386" \
        WINDRES="windres -Fpe-i386" \
        LDFLAGS="/MACHINE:X86" \
        LD="link" \
        NM="dumpbin -symbols" \
        STRIP=":" \
        AR="$HOME/msvc/ar-lib lib" \
        RANLIB=":"
        make
        make check
        make install
elif [ "${PlatformTarget}"=="x64" ]; then
    export PATH=`cygpath -u "${VCToolsInstallDir}"`/bin/Hostx64/x64:`cygpath -u "${WindowsSdkDir}"`bin/"${WindowsSDKVersion}"/x64:"$PATH"
    win32_target=_WIN32_WINNT_WIN7
    ./configure --host=x86_64-w64-mingw32 --prefix=/usr/local/msvc64 \
        CC="$HOME/msvc/compile cl -nologo" \
        CFLAGS="-MD /utf-8" \
        CXX="$HOME/msvc/compile cl -nologo" \
        CXXFLAGS="-MD /utf-8" \
        CPPFLAGS="-D_WIN32_WINNT=$win32_target" \
        RC="windres -Fpe-x86-64" \
        WINDRES="windres -Fpe-x86-64" \
        LDFLAGS="/MACHINE:X64" \
        LD="link" \
        NM="dumpbin -symbols" \
        STRIP=":" \
        AR="$HOME/msvc/ar-lib lib" \
        RANLIB=":"
        make
        make check
        make install
else
    echo Modify PlatformTarget value and run again.
    exit 1
fi