Fix Windows/MSYS2/MinGW64 build failures (issue #280)

Add MSYS environment support to configure.ac so users building from the
MSYS shell get proper Windows configuration (winsock2.h, ws2_32 lib)
instead of falling through to the Unix case (arpa/inet.h).

Changes:
- configure.ac: Add *-msys* case with Windows config and warning about
  msys-2.0.dll dependency
- configure.ac: Add host triplet and Windows build status to summary
- appveyor.yml: Add MSYS environment to CI matrix alongside MinGW64
- README.md: Add Windows/MSYS2 build section with step-by-step
  instructions and explanation of shell differences

Author: etr

README.md

@@ -119,6 +119,53 @@ Here are listed the libhttpserver specific options (the canonical configure opti
 
 [Back to TOC](#table-of-contents)
 
+### Building on Windows (MSYS2)
+
+MSYS2 provides multiple shell environments with different purposes. Understanding which shell to use is important:
+
+| Shell | Host Triplet | Runtime Dependency | Use Case |
+|-------|--------------|-------------------|----------|
+| **MinGW64** | `x86_64-w64-mingw32` | Native Windows | **Recommended** for native Windows apps |
+| **MSYS** | `x86_64-pc-msys` | msys-2.0.dll | POSIX-style apps, build tools |
+
+**Recommended: Use the MinGW64 shell** for building libhttpserver to produce native Windows binaries without additional runtime dependencies.
+
+#### Step-by-step build instructions
+
+1. Install [MSYS2](https://www.msys2.org/)
+
+2. Open the **MINGW64** shell (not the MSYS shell) from the Start Menu
+
+3. Install dependencies:
+```bash
+pacman -S --needed mingw-w64-x86_64-{gcc,libtool,make,pkg-config,doxygen,gnutls,curl} autotools
+```
+
+4. Build and install [libmicrohttpd](https://www.gnu.org/software/libmicrohttpd/) (>= 0.9.64)
+
+5. Build libhttpserver:
+```bash
+./bootstrap
+mkdir build && cd build
+../configure --disable-fastopen
+make
+make check  # run tests
+```
+
+**Important:** The `--disable-fastopen` flag is required on Windows as TCP_FASTOPEN is not supported.
+
+#### If you use the MSYS shell
+
+Building from the MSYS shell also works but the resulting binaries will depend on `msys-2.0.dll`. The configure script will display a warning when building in this environment. If you see:
+
+```
+configure: WARNING: Building from MSYS environment. Binaries will depend on msys-2.0.dll.
+```
+
+Consider switching to the MinGW64 shell for native Windows binaries.
+
+[Back to TOC](#table-of-contents)
+
 ## Getting Started
 The most basic example of creating a server and handling a requests for the path `/hello`:
 ```cpp

appveyor.yml

@@ -2,9 +2,15 @@ platform: x64
 
 environment:
   matrix:
-    - compiler: msys2
+    - compiler: mingw64
       MINGW_CHOST: x86_64-w64-mingw32
       MSYS2_ARCH: x86_64
+      MSYS2_SHELL: mingw64
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+    - compiler: msys
+      MINGW_CHOST: x86_64-pc-msys
+      MSYS2_ARCH: x86_64
+      MSYS2_SHELL: msys
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
 init:
   - 'echo Building libhttpserver %version% for Windows'
@@ -15,13 +21,18 @@ init:
   - 'echo Cygwin root is: %CYG_ROOT%'
   - ps: iex ((new-object net.webclient).DownloadString('https://raw.githubusercontent.com/appveyor/ci/master/scripts/enable-rdp.ps1'))
 install:
-  - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -msys2 -c "pacman --noconfirm -S --needed mingw-w64-$MSYS2_ARCH-{libtool,make,pkg-config,libsystre,doxygen,gnutls,graphviz,curl}"'
-  - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -msys2 -c "pacman --noconfirm -S --needed autotools"'
-  - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -mingw64 -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER && curl https://s3.amazonaws.com/libhttpserver/libmicrohttpd_releases/libmicrohttpd-0.9.64.tar.gz -o libmicrohttpd-0.9.64.tar.gz"'
-  - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -mingw64 -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER && tar -xzf libmicrohttpd-0.9.64.tar.gz"'
-  - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -mingw64 -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER/libmicrohttpd-0.9.64 && ./configure --disable-examples --enable-poll=no --prefix /C/msys64 && make && make install"'
-  - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -mingw64 -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER && ./bootstrap"'
-  - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -mingw64 -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER && mkdir build && cd build && MANIFEST_TOOL=no; ../configure --disable-fastopen --prefix /C/msys64 CXXFLAGS=-I/C/msys64/include LDFLAGS=-L/C/msys64/lib; make"'
+  # Install packages (use msys2 shell for package management)
+  - 'C:\msys64\msys2_shell.cmd -defterm -no-start -msys2 -c "pacman --noconfirm -S --needed mingw-w64-$MSYS2_ARCH-{libtool,make,pkg-config,libsystre,doxygen,gnutls,graphviz,curl}"'
+  - 'C:\msys64\msys2_shell.cmd -defterm -no-start -msys2 -c "pacman --noconfirm -S --needed autotools"'
+  # For msys shell, also install msys-specific packages
+  - 'if "%compiler%"=="msys" C:\msys64\msys2_shell.cmd -defterm -no-start -msys2 -c "pacman --noconfirm -S --needed msys2-devel gcc make curl"'
+  # Download and build libmicrohttpd
+  - 'C:\msys64\msys2_shell.cmd -defterm -no-start -%MSYS2_SHELL% -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER && curl https://s3.amazonaws.com/libhttpserver/libmicrohttpd_releases/libmicrohttpd-0.9.64.tar.gz -o libmicrohttpd-0.9.64.tar.gz"'
+  - 'C:\msys64\msys2_shell.cmd -defterm -no-start -%MSYS2_SHELL% -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER && tar -xzf libmicrohttpd-0.9.64.tar.gz"'
+  - 'C:\msys64\msys2_shell.cmd -defterm -no-start -%MSYS2_SHELL% -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER/libmicrohttpd-0.9.64 && ./configure --disable-examples --enable-poll=no --prefix /C/msys64 && make && make install"'
+  # Bootstrap and configure libhttpserver
+  - 'C:\msys64\msys2_shell.cmd -defterm -no-start -%MSYS2_SHELL% -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER && ./bootstrap"'
+  - 'C:\msys64\msys2_shell.cmd -defterm -no-start -%MSYS2_SHELL% -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER && mkdir build && cd build && MANIFEST_TOOL=no; ../configure --disable-fastopen --prefix /C/msys64 CXXFLAGS=-I/C/msys64/include LDFLAGS=-L/C/msys64/lib; make"'
 build_script:
-  - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -mingw64 -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER/build && make check"'
-  - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -mingw64 -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER/build && cat test/test-suite.log"'
+  - 'C:\msys64\msys2_shell.cmd -defterm -no-start -%MSYS2_SHELL% -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER/build && make check"'
+  - 'C:\msys64\msys2_shell.cmd -defterm -no-start -%MSYS2_SHELL% -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER/build && cat test/test-suite.log"'

configure.ac

@@ -71,6 +71,16 @@ case "$host" in
         NETWORK_LIBS="-lws2_32"
         native_srcdir=$(cd $srcdir; pwd -W)
         ;;
+    *-msys*)
+        AC_MSG_WARN([
+Building from MSYS environment. Binaries will depend on msys-2.0.dll.
+For native Windows binaries, use the MinGW64 shell instead.
+])
+        NETWORK_HEADER="winsock2.h"
+        ADDITIONAL_LIBS="-lpthread -no-undefined"
+        NETWORK_LIBS="-lws2_32"
+        native_srcdir=$(cd $srcdir; pwd -W)
+        ;;
     *-cygwin*)
         NETWORK_HEADER="arpa/inet.h"
         ADDITIONAL_LIBS="-lpthread -no-undefined"
@@ -294,11 +304,13 @@ AC_OUTPUT(
 
 AC_MSG_NOTICE([Configuration Summary:
   Operating System:  ${host_os}
+  Host triplet    :  ${host}
   Target directory:  ${prefix}
   License         :  LGPL only
   Debug	          :  ${debugit}
   TLS Enabled     :  ${have_gnutls}
   TCP_FASTOPEN    :  ${is_fastopen_supported}
   Static          :  ${static}
+  Windows build   :  ${is_windows}
   Build examples  :  ${enable_examples}
 ])