Add option to build for older Windows versions

Adds configuration checks for Windows API functions, and a win_ver
configuration option to change the targeted API version.

3 files changed, 81 insertions, 22 deletions

diff --git a/src/ring.c b/src/ring.c
index 4341906..cb8a47e 100644
--- a/src/ring.c
+++ b/src/ring.c
@@ -9,7 +9,7 @@
 #include <zix/allocator.h>
 #include <zix/status.h>
 
-#if defined(_WIN32)
+#if USE_VIRTUALLOCK
 #  include <windows.h>
 #elif USE_MLOCK
 #  include <sys/mman.h>
@@ -108,7 +108,7 @@ zix_ring_free(ZixRing* const ring)
 ZixStatus
 zix_ring_mlock(ZixRing* const ring)
 {
-#if defined(_WIN32)
+#if USE_VIRTUALLOCK
   return (VirtualLock(ring, sizeof(ZixRing)) &&
           VirtualLock(ring->buf, ring->size))
            ? ZIX_STATUS_SUCCESS
@@ -119,6 +119,7 @@ zix_ring_mlock(ZixRing* const ring)
                              mlock(ring->buf, ring->size));
 
 #else
+  (void)ring;
   return ZIX_STATUS_NOT_SUPPORTED;
 #endif
 }
diff --git a/src/win32/filesystem_win32.c b/src/win32/filesystem_win32.c
index d26d789..d311bf8 100644
--- a/src/win32/filesystem_win32.c
+++ b/src/win32/filesystem_win32.c
@@ -183,13 +183,14 @@ zix_file_unlock(FILE* const file, const ZixFileLockMode mode)
 char*
 zix_canonical_path(ZixAllocator* const allocator, const char* const path)
 {
-  char full[MAX_PATH] = {0};
-  if (!path || !GetFullPathName(path, MAX_PATH, full, NULL)) {
+  if (!path) {
     return NULL;
   }
 
+#if USE_GETFINALPATHNAMEBYHANDLE // Vista+
+
   const HANDLE h =
-    CreateFile(full,
+    CreateFile(path,
                FILE_READ_ATTRIBUTES,
                FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
                NULL,
@@ -197,27 +198,39 @@ zix_canonical_path(ZixAllocator* const allocator, const char* const path)
                FILE_FLAG_BACKUP_SEMANTICS,
                NULL);
 
-  const DWORD flags      = FILE_NAME_NORMALIZED | VOLUME_NAME_DOS;
-  const DWORD final_size = GetFinalPathNameByHandle(h, NULL, 0U, flags);
-  if (!final_size) {
-    CloseHandle(h);
+  if (h == INVALID_HANDLE_VALUE) {
     return NULL;
   }
 
-  char* const final = (char*)zix_calloc(allocator, (size_t)final_size + 1U, 1U);
-  if (!final || !GetFinalPathNameByHandle(h, final, final_size + 1U, flags)) {
-    zix_free(allocator, final);
-    CloseHandle(h);
-    return NULL;
-  }
-
-  if (final_size > 4U && !strncmp(final, "\\\\?\\", 4)) {
-    memmove(final, final + 4U, final_size - 4U);
-    final[final_size - 4U] = '\0';
+  const DWORD flags  = FILE_NAME_NORMALIZED | VOLUME_NAME_DOS;
+  const DWORD length = GetFinalPathNameByHandle(h, NULL, 0U, flags);
+  TCHAR*      final  = NULL;
+  if (length) {
+    final = (TCHAR*)zix_calloc(allocator, (size_t)length + 1U, sizeof(TCHAR));
+    if (final) {
+      GetFinalPathNameByHandle(h, final, length + 1U, flags);
+    }
   }
 
   CloseHandle(h);
   return final;
+
+#else // Fall back to "full path iff it exists" for older Windows
+
+  TCHAR* full = NULL;
+  if (GetFileAttributes(path) != INVALID_FILE_ATTRIBUTES) {
+    const DWORD length = GetFullPathName(path, 0U, NULL, NULL);
+    if (length) {
+      full = (TCHAR*)zix_calloc(allocator, (size_t)length + 1U, sizeof(TCHAR));
+      if (full) {
+        GetFullPathName(path, length + 1U, full, NULL);
+      }
+    }
+  }
+
+  return full;
+
+#endif
 }
 
 static ZixFileType
@@ -312,7 +325,13 @@ zix_create_directory_symlink(const char* const target_path,
 ZixStatus
 zix_create_hard_link(const char* const target_path, const char* const link_path)
 {
+#if USE_CREATEHARDLINK
   return zix_windows_status(CreateHardLink(link_path, target_path, NULL));
+#else
+  (void)target_path;
+  (void)link_path;
+  return ZIX_STATUS_NOT_SUPPORTED;
+#endif
 }
 
 char*
diff --git a/src/zix_config.h b/src/zix_config.h
index 0aab586..6bbc92b 100644
--- a/src/zix_config.h
+++ b/src/zix_config.h
@@ -1,4 +1,4 @@
-// Copyright 2021-2023 David Robillard <d@drobilla.net>
+// Copyright 2021-2024 David Robillard <d@drobilla.net>
 // SPDX-License-Identifier: ISC
 
 /*
@@ -78,9 +78,16 @@
 #    endif
 #  endif
 
-// Windows: CreateSymbolicLink()
+// Windows XP: CreateHardLink()
+#  ifndef HAVE_CREATEHARDLINK
+#    if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x0501
+#      define HAVE_CREATEHARDLINK 1
+#    endif
+#  endif
+
+// Windows Vista: CreateSymbolicLink()
 #  ifndef HAVE_CREATESYMBOLICLINK
-#    if defined(_MSC_VER) && _MSC_VER >= 1910
+#    if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x0600 && !defined(__MINGW32__)
 #      define HAVE_CREATESYMBOLICLINK 1
 #    endif
 #  endif
@@ -99,6 +106,13 @@
 #    endif
 #  endif
 
+// Windows Vista: GetFinalPathNameByHandle()
+#  ifndef HAVE_GETFINALPATHNAMEBYHANDLE
+#    if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x0600
+#      define HAVE_GETFINALPATHNAMEBYHANDLE 1
+#    endif
+#  endif
+
 // POSIX.1-2001: mlock()
 #  ifndef HAVE_MLOCK
 #    if ZIX_POSIX_VERSION >= 200112L
@@ -148,6 +162,13 @@
 #    endif
 #  endif
 
+// Windows XP: VirtualLock
+#  ifndef HAVE_VIRTUALLOCK
+#    if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x0501
+#      define HAVE_VIRTUALLOCK 1
+#    endif
+#  endif
+
 #endif // !defined(ZIX_NO_DEFAULT_CONFIG)
 
 /*
@@ -176,6 +197,12 @@
 #  define USE_COPY_FILE_RANGE 0
 #endif
 
+#if defined(HAVE_CREATEHARDLINK) && HAVE_CREATEHARDLINK
+#  define USE_CREATEHARDLINK 1
+#else
+#  define USE_CREATEHARDLINK 0
+#endif
+
 #if defined(HAVE_CREATESYMBOLICLINK) && HAVE_CREATESYMBOLICLINK
 #  define USE_CREATESYMBOLICLINK 1
 #else
@@ -194,6 +221,12 @@
 #  define USE_FLOCK 0
 #endif
 
+#if defined(HAVE_GETFINALPATHNAMEBYHANDLE) && HAVE_GETFINALPATHNAMEBYHANDLE
+#  define USE_GETFINALPATHNAMEBYHANDLE 1
+#else
+#  define USE_GETFINALPATHNAMEBYHANDLE 0
+#endif
+
 #if defined(HAVE_MLOCK) && HAVE_MLOCK
 #  define USE_MLOCK 1
 #else
@@ -236,4 +269,10 @@
 #  define USE_SYSCONF 0
 #endif
 
+#if defined(HAVE_VIRTUALLOCK) && HAVE_VIRTUALLOCK
+#  define USE_VIRTUALLOCK 1
+#else
+#  define USE_VIRTUALLOCK 0
+#endif
+
 #endif // ZIX_CONFIG_H