Target POSIX API by default when building with Emscripten.

This allows to enable more POSIX APIs when building with Emscripten
by default. Users may switch to WASI API by defining
BOOST_FILESYSTEM_EMSCRIPTEN_USE_WASI config macro.

Originally implemented in and based on
#233.

Author: Lastique

CMakeLists.txt

@@ -19,6 +19,7 @@ set(BOOST_FILESYSTEM_DISABLE_STATX OFF CACHE BOOL "Disable usage of statx API in
 set(BOOST_FILESYSTEM_DISABLE_GETRANDOM OFF CACHE BOOL "Disable usage of getrandom API in Boost.Filesystem")
 set(BOOST_FILESYSTEM_DISABLE_ARC4RANDOM OFF CACHE BOOL "Disable usage of arc4random API in Boost.Filesystem")
 set(BOOST_FILESYSTEM_DISABLE_BCRYPT OFF CACHE BOOL "Disable usage of BCrypt API in Boost.Filesystem")
+set(BOOST_FILESYSTEM_EMSCRIPTEN_USE_WASI OFF CACHE BOOL "Use WASI under Emscripten in Boost.Filesystem")
 
 # Note: We can't use the Boost::library targets in the configure checks as they may not yet be included
 # by the superproject when this CMakeLists.txt is included. We also don't want to hardcode include paths
@@ -131,6 +132,9 @@ endif()
 if(BOOST_FILESYSTEM_DISABLE_BCRYPT)
     target_compile_definitions(boost_filesystem PRIVATE BOOST_FILESYSTEM_DISABLE_BCRYPT)
 endif()
+if(BOOST_FILESYSTEM_EMSCRIPTEN_USE_WASI)
+    target_compile_definitions(boost_filesystem PRIVATE BOOST_FILESYSTEM_EMSCRIPTEN_USE_WASI)
+endif()
 
 if(BOOST_FILESYSTEM_HAS_STAT_ST_BLKSIZE)
     target_compile_definitions(boost_filesystem PRIVATE BOOST_FILESYSTEM_HAS_STAT_ST_BLKSIZE)

doc/index.htm

@@ -312,8 +312,13 @@ <h2><a name="Macros">Macros</a></h2>
     <td valign="top">Not defined. BCrypt API presence detected at library build time.</td>
     <td valign="top">Boost.Filesystem library does not use the BCrypt API on Windows. Has no effect on other platforms.</td>
   </tr>
+  <tr>
+    <td valign="top"><code>BOOST_FILESYSTEM_EMSCRIPTEN_USE_WASI</code></td>
+    <td valign="top">Not defined. When building with <a href="https://emscripten.org/">Emscripten</a>, target POSIX API.</td>
+    <td valign="top">Boost.Filesystem library targets WASI API instead of POSIX when building with <a href="https://emscripten.org/">Emscripten</a>. Has no effect on other platforms.</td>
+  </tr>
 </table>
-<p>User-defined BOOST_POSIX_API and BOOST_WINDOWS_API macros are no longer
+<p>User-defined <code>BOOST_POSIX_API</code> and <code>BOOST_WINDOWS_API</code> macros are no longer
 supported.</p>
 <h2><a name="Building">Building</a> the object-library</h2>
 <p>The object-library will  be built automatically if you are using the Boost
@@ -330,7 +335,7 @@ <h2><a name="Building">Building</a> the object-library</h2>
 operating systems or embedded operating systems, support POSIX compatible file
 systems and so will work with the Filesystem Library.</p>
 <p>The object-library can be built for static or dynamic (shared/dll) linking.
-This is controlled by the BOOST_ALL_DYN_LINK or BOOST_FILESYSTEM_DYN_LINK
+This is controlled by the <code>BOOST_ALL_DYN_LINK</code> or <code>BOOST_FILESYSTEM_DYN_LINK</code>
 macros. See the <a href="http://www.boost.org/development/separate_compilation.html">Separate
 Compilation</a> page for a description of the techniques used.</p>
 <h3>Note for <a name="Cygwin">Cygwin</a> users</h3>
@@ -488,7 +493,7 @@ <h3>Version 1</h3>
 <hr>
 
 <p>&copy; Copyright Beman Dawes, 2002-2005</p>
-<p>&copy; Copyright Andrey Semashev, 2021</p>
+<p>&copy; Copyright Andrey Semashev, 2021-2022</p>
 <p> Use, modification, and distribution are subject to the Boost Software
 License, Version 1.0. See <a href="http://www.boost.org/LICENSE_1_0.txt">
 www.boost.org/LICENSE_1_0.txt</a></p>

doc/release_history.html

@@ -41,6 +41,7 @@
 
 <h2>1.80.0</h2>
 <ul>
+  <li>When building with <a href="https://emscripten.org/">Emscripten</a>, target POSIX API by default. Users can define <code>BOOST_FILESYSTEM_EMSCRIPTEN_USE_WASI</code> to target WASI API instead. (<a href="https://github.com/boostorg/filesystem/pull/233">PR#233</a>)</li>
   <li>On Windows, added a fallback implementation for querying file attributes in case if the file cannot be opened with <code>ERROR_ACCESS_DENIED</code> error. This may allow <code>status</code> and <code>symlink_status</code> to succeed for system files and directories that are not reparse points or symlinks. (<a href="https://github.com/boostorg/filesystem/issues/234">#234</a>)</li>
   <li>On Windows, added a workaround for <code>status</code> and <code>symlink_status</code> reporting that files do not exist on FAT/exFAT filesystems. (<a href="https://github.com/boostorg/filesystem/issues/236">#236</a>)</li>
 </ul>

src/operations.cpp

@@ -38,12 +38,17 @@
 #endif
 #include <cerrno>
 
+// Default to POSIX under Emscripten. If BOOST_FILESYSTEM_EMSCRIPTEN_USE_WASI is set, use WASI instead.
+#if defined(__wasm) && (!defined(__EMSCRIPTEN__) || defined(BOOST_FILESYSTEM_EMSCRIPTEN_USE_WASI))
+#define BOOST_FILESYSTEM_USE_WASI
+#endif
+
 #ifdef BOOST_POSIX_API
 
 #include <sys/types.h>
 #include <sys/stat.h>
 
-#if defined(__wasm)
+#if defined(BOOST_FILESYSTEM_USE_WASI)
 // WASI does not have statfs or statvfs.
 #elif !defined(__APPLE__) && \
     (!defined(__OpenBSD__) || BOOST_OS_BSD_OPEN >= BOOST_VERSION_NUMBER(4, 4, 0)) && \
@@ -2220,7 +2225,7 @@ bool copy_file(path const& from, path const& to, unsigned int options, error_cod
     }
 
     mode_t to_mode = from_mode;
-#if !defined(__wasm)
+#if !defined(BOOST_FILESYSTEM_USE_WASI)
     // Enable writing for the newly created files. Having write permission set is important e.g. for NFS,
     // which checks the file permission on the server, even if the client's file descriptor supports writing.
     to_mode |= S_IWUSR;
@@ -2339,7 +2344,7 @@ bool copy_file(path const& from, path const& to, unsigned int options, error_cod
     if (BOOST_UNLIKELY(err != 0))
         goto fail; // err already contains the error code
 
-#if !defined(__wasm)
+#if !defined(BOOST_FILESYSTEM_USE_WASI)
     // If we created a new file with an explicitly added S_IWUSR permission,
     // we may need to update its mode bits to match the source file.
     if (to_mode != from_mode)
@@ -2775,7 +2780,7 @@ void create_symlink(path const& to, path const& from, error_code* ec)
 BOOST_FILESYSTEM_DECL
 path current_path(error_code* ec)
 {
-#if defined(UNDER_CE) || defined(__wasm)
+#if defined(UNDER_CE) || defined(BOOST_FILESYSTEM_USE_WASI)
     // Windows CE has no current directory, so everything's relative to the root of the directory tree.
     // WASI also does not support current path.
     emit_error(BOOST_ERROR_NOT_SUPPORTED, ec, "boost::filesystem::current_path");
@@ -2845,7 +2850,7 @@ path current_path(error_code* ec)
 BOOST_FILESYSTEM_DECL
 void current_path(path const& p, system::error_code* ec)
 {
-#if defined(UNDER_CE) || defined(__wasm)
+#if defined(UNDER_CE) || defined(BOOST_FILESYSTEM_USE_WASI)
     emit_error(BOOST_ERROR_NOT_SUPPORTED, p, ec, "boost::filesystem::current_path");
 #else
     error(!BOOST_SET_CURRENT_DIRECTORY(p.c_str()) ? BOOST_ERRNO : 0, p, ec, "boost::filesystem::current_path");
@@ -3349,7 +3354,7 @@ void permissions(path const& p, perms prms, system::error_code* ec)
     if ((prms & add_perms) && (prms & remove_perms)) // precondition failed
         return;
 
-#if defined(__wasm)
+#if defined(BOOST_FILESYSTEM_USE_WASI)
     emit_error(BOOST_ERROR_NOT_SUPPORTED, p, ec, "boost::filesystem::permissions");
 #elif defined(BOOST_POSIX_API)
     error_code local_ec;
@@ -3613,7 +3618,7 @@ space_info space(path const& p, error_code* ec)
     if (ec)
         ec->clear();
 
-#if defined(__wasm)
+#if defined(BOOST_FILESYSTEM_USE_WASI)
 
     emit_error(BOOST_ERROR_NOT_SUPPORTED, p, ec, "boost::filesystem::space");