Add Windows compatibility support

[AliRezaBeigy]

Adds comprehensive Windows build support to picoquic, enabling compilation on Windows using MSVC, MinGW, and other Windows toolchains.

Changes

Core Windows Compatibility

• picoquic/wincompat.c: New file implementing wintimeofday() function, providing a Windows-compatible implementation of gettimeofday() for picotls and picoquic
• picoquic/wincompat.h: Enhanced to:
  • Automatically define _WINDOWS macro when Windows is detected via standard macros (_WIN32, __WIN32__, __MINGW32__, etc.)
  • Include <ws2tcpip.h> for IPv6 socket structures (sockaddr_in6, etc.)
  • Provide gettimeofday macro mapping to wintimeofday

Build System Updates

• CMakeLists.txt:
  • Added wincompat.c to picoquic-core library sources when building on Windows
  • When PICOQUIC_FETCH_PTLS=ON, automatically provides Windows compatibility files to picotls:
    • Copies wincompat.h to picotls include directory
    • Copies wincompat.c to picotls lib directory
    • Adds wincompat.c to picotls-core target
• picoquic/picoquic.vcxproj: Added wincompat.c to Visual Studio project
• picoquic/picoquic.vcxproj.filters: Added wincompat.c to Source Files filter

Header File Updates

• picoquic/picoquic.h: Added early _WINDOWS detection to ensure correct header inclusion order
• picoquic/picosocks.h: Added early _WINDOWS detection
• picoquic/picoquic_packet_loop.h: Added ssize_t type definition for Windows compatibility

Why This Is Needed

1. Missing gettimeofday(): Windows doesn't provide gettimeofday(), which is required by picotls. The wintimeofday() implementation converts Windows FILETIME to Unix timeval.

2. IPv6 Support: Windows requires <ws2tcpip.h> for IPv6 socket structures, which was missing from the compatibility header.

3. Build Integration: The existing wincompat.h and wincompat.c files weren't being compiled into the library, causing link errors on Windows.

Backward Compatibility

• No changes to existing Unix/Linux builds
• All changes are Windows-specific (#ifdef _WINDOWS or if(WIN32))
• Existing code using #ifdef _WINDOWS continues to work without modification

[Mygod]

@codex review

[Mygod]

Some findings that I accidentally produced:

• High: ssize_t is defined in two incompatible ways on Windows. picoquic/wincompat.h:30 defines it as a macro (#define ssize_t int), while picoquic/picoquic_packet_loop.h:33-39 adds typedef int ssize_t;. If any TU includes wincompat.h before picoquic_packet_loop.h, the macro expands to typedef int int; and fails to compile. Even when it compiles, int is the wrong width for 64‑bit Windows. Suggestion: centralize ssize_t in wincompat.h with #include <BaseTsd.h> and typedef SSIZE_T ssize_t;, set _SSIZE_T_DEFINED, and remove the new block from picoquic/picoquic_packet_loop.h.
• Medium: struct timezone can be redefined if wincompat.h is force‑included as the comment claims. picoquic/wincompat.c:15-22 defines struct timezone behind _TIMEZONE_DEFINED, but picoquic/wincompat.h:47-52 defines it without setting that guard. If /FIwincompat.h is used, wincompat.c will re‑define the struct. Suggestion: include picoquic/wincompat.h in picoquic/wincompat.c and remove the local struct, or add _TIMEZONE_DEFINED in the header.
• Medium: The picotls wiring may not actually fix Windows builds. In CMakeLists.txt:234-245 you copy wincompat.{h,c} into picotls and add the C file, but you never force-include wincompat.h for picotls, so gettimeofday calls in picotls (if any) may still be unresolved or using the wrong signature. Suggestion: explicitly force-include wincompat.h for picotls-core or patch picotls to include it on Windows.

[Copilot]

Pull request overview

This PR adds comprehensive Windows build support to picoquic, enabling compilation using MSVC, MinGW, and other Windows toolchains. It implements the missing gettimeofday() function for Windows through wintimeofday() and ensures proper header inclusion for Windows networking APIs.

Changes:

• Implements wintimeofday() function to provide Windows-compatible gettimeofday() functionality
• Updates headers to auto-detect Windows platform and define _WINDOWS macro consistently
• Integrates Windows compatibility files into build systems (CMake and Visual Studio projects)

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
picoquic/wincompat.c	New implementation of wintimeofday() function that converts Windows FILETIME to Unix timeval
picoquic/wincompat.h	Enhanced with automatic _WINDOWS detection, ws2tcpip.h inclusion, and gettimeofday macro mapping
picoquic/picoquic.h	Added early _WINDOWS detection for correct header ordering
picoquic/picosocks.h	Added early _WINDOWS detection for consistency
picoquic/picoquic_packet_loop.h	Added Windows-specific ssize_t typedef and Windows-compatible function signature for picoquic_packet_loop_v3
CMakeLists.txt	Added wincompat.c to build on Windows and provides compatibility files to fetched picotls dependency
picoquic/picoquic.vcxproj	Added wincompat.c to Visual Studio project sources
picoquic/picoquic.vcxproj.filters	Added wincompat.c to Source Files filter

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Bravo.

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[Mygod]

The changes still seem questionable to me. For example, "Missing gettimeofday()" is not true since the repo does contain an implementation so we should not reinvent the wheel.

[AliRezaBeigy]

@Mygod Thank you for the review. I've researched the issues raised:

1. Regarding "gettimeofday already exists", I checked the upstream repositories and wincompat.c does NOT exist there. While wincompat.h declares wintimeofday(), there is no implementation anywhere in the upstream repo.

2. Thanks for fixing the ssize_t incompatible definitions issue and addressing the struct timezone redefinition issue.

I made some additional changes:

1. In CMakeLists.txt, we now force-include wincompat.h for ALL picotls targets, not just picotls-core, because other picotls components also need the Windows compatibility definitions. Without this change, the build failed.

2. The _WINDOWS macro definition has been removed from CMakeLists.txt because it didn't work and still in the compilation I got error that compiler try to include non windows header. I've added the -D_WINDOWS option directly in the cc arguments in the slipstream-ffi build code instead. Mygod/slipstream-rust@c3dc75e

[Mygod]

It exists in picotls. Please refer to my comment in the other PR.

[AliRezaBeigy]

@Mygod Thanks for the pointer. I’ve switched to picotls’ wintimeofday.c and dropped the duplicate in picoquic. All tests pass.