xref: /aosp_15_r20/external/curl/winbuild/README.md (revision 6236dae45794135f37c4eb022389c904c8b0090d)

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# Building curl with Visual C++

 This document describes how to compile, build and install curl and libcurl
 from sources using the Visual C++ build tool. To build with VC++, you will of
 course have to first install VC++. The minimum required version of VC is 6
 (part of Visual Studio 6). However using a more recent version is strongly
 recommended.

 VC++ is also part of the Windows Platform SDK. You do not have to install the
 full Visual Studio or Visual C++ if all you want is to build curl.

 The latest Platform SDK can be downloaded freely from [Windows SDK and
 emulator
 archive](https://developer.microsoft.com/en-us/windows/downloads/sdk-archive)

## Prerequisites

 If you wish to support zlib, OpenSSL, c-ares, ssh2, you will have to download
 them separately and copy them to the `deps` directory as shown below:

    somedirectory\
     |_curl-src
     | |_winbuild
     |
     |_deps
       |_ lib
       |_ include
       |_ bin

 It is also possible to create the `deps` directory in some other random places
 and tell the `Makefile` its location using the `WITH_DEVEL` option.

## Building straight from git

 When you check out code git and build it, as opposed from a released source
 code archive, you need to first run the `buildconf.bat` batch file (present
 in the source code root directory) to set things up.

## Open a command prompt

Open a Visual Studio Command prompt:

 Using the **'VS [version] [platform] [type] Command Prompt'** menu entry:
 where [version] is the Visual Studio version, [platform] is e.g. x64 and
 [type] Native or Cross platform build. This type of command prompt may not
 exist in all Visual Studio versions. For example, to build a 64-bit curl open
 the x64 Native Tools prompt.

 See also:

 [How to: Enable a 64-Bit, x64 hosted MSVC toolset on the command line](https://docs.microsoft.com/en-us/cpp/build/how-to-enable-a-64-bit-visual-cpp-toolset-on-the-command-line)

 [Set the Path and Environment Variables for Command-Line Builds](https://docs.microsoft.com/en-us/cpp/build/building-on-the-command-line)

 [Developer Command Prompt for Visual Studio](https://docs.microsoft.com/en-us/dotnet/framework/tools/developer-command-prompt-for-vs)

## Build in the console

 Once you are in the console, go to the winbuild directory in the Curl
 sources:

    cd curl-src\winbuild

 Then you can call `nmake /f Makefile.vc` with the desired options (see
 below). The builds will be in the top src directory, `builds\` directory, in
 a directory named using the options given to the nmake call.

    nmake /f Makefile.vc mode=<static or dll> <options>

where `<options>` is one or many of:

 - `VC=<num>`                    - VC version. 6 or later.
 - `WITH_DEVEL=<path>`           - Paths for the development files (SSL, zlib, etc.)
                                   Defaults to sibling directory: `../deps`
 - `WITH_SSL=<dll/static>`       - Enable OpenSSL support, DLL or static
 - `WITH_NGHTTP2=<dll/static>`   - Enable HTTP/2 support, DLL or static
 - `WITH_MSH3=<dll/static>`      - Enable (experimental) HTTP/3 support, DLL or static
 - `WITH_MBEDTLS=<dll/static>`   - Enable mbedTLS support, DLL or static
 - `WITH_WOLFSSL=<dll/static>`   - Enable wolfSSL support, DLL or static
 - `WITH_CARES=<dll/static>`     - Enable c-ares support, DLL or static
 - `WITH_ZLIB=<dll/static>`      - Enable zlib support, DLL or static
 - `WITH_SSH=<dll/static>`       - Enable libssh support, DLL or static
 - `WITH_SSH2=<dll/static>`      - Enable libssh2 support, DLL or static
 - `WITH_PREFIX=<dir>`           - Where to install the build
 - `ENABLE_SSPI=<yes/no>`        - Enable SSPI support, defaults to yes
 - `ENABLE_IPV6=<yes/no>`        - Enable IPv6, defaults to yes
 - `ENABLE_IDN=<yes or no>`      - Enable use of Windows IDN APIs, defaults to yes
                                   Requires Windows Vista or later
 - `ENABLE_SCHANNEL=<yes/no>`    - Enable native Windows SSL support, defaults
                                   to yes if SSPI and no other SSL library
 - `ENABLE_OPENSSL_AUTO_LOAD_CONFIG=<yes/no>`
                                 - Enable loading OpenSSL configuration
                                   automatically, defaults to yes
 - `ENABLE_UNICODE=<yes/no>`     - Enable Unicode support, defaults to no
 - `GEN_PDB=<yes/no>`            - Generate External Program Database
                                   (debug symbols for release build)
 - `DEBUG=<yes/no>`              - Debug builds
 - `MACHINE=<x86/x64/arm64>`     - Target architecture (default is x86)
 - `CARES_PATH=<path>`           - Custom path for c-ares
 - `MBEDTLS_PATH=<path>`         - Custom path for mbedTLS
 - `WOLFSSL_PATH=<path>`         - Custom path for wolfSSL
 - `NGHTTP2_PATH=<path>`         - Custom path for nghttp2
 - `MSH3_PATH=<path>`            - Custom path for msh3
 - `SSH2_PATH=<path>`            - Custom path for libssh2
 - `SSL_PATH=<path>`             - Custom path for OpenSSL
 - `ZLIB_PATH=<path>`            - Custom path for zlib

## Cleaning a build

 For most build configurations you can remove a bad build by using the same
 options with the added keyword "clean". For example:

    nmake /f Makefile.vc mode=static clean

 Build errors due to switching Visual Studio platform tools or mistakenly
 specifying the wrong machine platform for the tools can usually be solved by
 first cleaning the bad build.

## Static linking of Microsoft's C runtime (CRT):

 If you are using mode=static nmake will create and link to the static build
 of libcurl but *not* the static CRT. If you must you can force nmake to link
 in the static CRT by passing `RTLIBCFG=static`. Typically you shouldn't use
 that option, and nmake will default to the DLL CRT. `RTLIBCFG` is rarely used
 and therefore rarely tested. When passing `RTLIBCFG` for a configuration that
 was already built but not with that option, or if the option was specified
 differently, you must destroy the build directory containing the
 configuration so that nmake can build it from scratch.

 This option is not recommended unless you have enough development experience
 to know how to match the runtime library for linking (that is, the CRT). If
 `RTLIBCFG=static` then release builds use `/MT` and debug builds use `/MTd`.

## Building your own application with libcurl (Visual Studio example)

 When you build curl and libcurl, nmake will show the relative path where the
 output directory is. The output directory is named from the options nmake used
 when building. You may also see temp directories of the same name but with
 suffixes -obj-curl and -obj-lib.

 For example let's say you've built curl.exe and libcurl.dll from the Visual
 Studio 2010 x64 Win64 Command Prompt:

    nmake /f Makefile.vc mode=dll VC=10

 The output directory will have a name similar to
 `..\builds\libcurl-vc10-x64-release-dll-ipv6-sspi-schannel`.

 The output directory contains subdirectories bin, lib and include. Those are
 the directories to set in your Visual Studio project. You can either copy the
 output directory to your project or leave it in place. Following the example,
 let's assume you leave it in place and your curl top source directory is
 `C:\curl-7.82.0`. You would set these options for configurations using the
 x64 platform:

~~~
 - Configuration Properties > Debugging > Environment
    PATH=C:\curl-7.82.0\builds\libcurl-vc10-x64-release-dll-ipv6-sspi-schannel\bin;%PATH%

 - C/C++ > General > Additional Include Directories
    C:\curl-7.82.0\builds\libcurl-vc10-x64-release-dll-ipv6-sspi-schannel\include;

 - Linker > General > Additional Library Directories
    C:\curl-7.82.0\builds\libcurl-vc10-x64-release-dll-ipv6-sspi-schannel\lib;

 - Linker > Input > Additional Dependencies
    libcurl.lib;
~~~

 For configurations using the x86 platform (aka Win32 platform) you would
 need to make a separate x86 build of libcurl.

 If you build libcurl static (`mode=static`) or debug (`DEBUG=yes`) then the
 library name will vary and separate builds may be necessary for separate
 configurations of your project within the same platform. This is discussed in
 the next section.

## Building your own application with a static libcurl

 When building an application that uses the static libcurl library on Windows,
 you must define `CURL_STATICLIB`. Otherwise the linker will look for dynamic
 import symbols.

 The static library name has an `_a` suffix in the basename and the debug
 library name has a `_debug` suffix in the basename. For example,
 `libcurl_a_debug.lib` is a static debug build of libcurl.

 You may need a separate build of libcurl for each VC configuration combination
 (for example: Debug|Win32, Debug|x64, Release|Win32, Release|x64).

 You must specify any additional dependencies needed by your build of static
 libcurl (for example:
 `advapi32.lib;crypt32.lib;normaliz.lib;ws2_32.lib;wldap32.lib`).

## Legacy Windows and SSL

 When you build curl using the build files in this directory the default SSL
 backend will be Schannel (Windows SSPI), the native SSL library that comes
 with the Windows OS. Schannel in Windows 8 and earlier is not able to connect
 to servers that no longer support the legacy handshakes and algorithms used by
 those versions. If you will be using curl in one of those earlier versions of
 Windows you should choose another SSL backend like OpenSSL.