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-rw-r--r--libbutl/filesystem.cxx83
-rw-r--r--libbutl/filesystem.mxx21
2 files changed, 51 insertions, 53 deletions
diff --git a/libbutl/filesystem.cxx b/libbutl/filesystem.cxx
index d453006..ea084b9 100644
--- a/libbutl/filesystem.cxx
+++ b/libbutl/filesystem.cxx
@@ -909,52 +909,53 @@ namespace butl
{
using namespace win32;
- if (!dir)
- {
- // Try to create a regular symbolic link without elevated privileges by
- // passing the new SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE flag.
- // The flag is new and it may not be defined at compile-time so we pass
- // its literal value.
- //
- // We may also be running on an earlier version of Windows (before 10
- // build 14972) that doesn't support it. The natural way to handle that
- // would have been to check the build of Windows that we are running on
- // but that turns out to not be that easy (requires a deprecated API,
- // specific executable manifest setup, a dance on one leg, and who knows
- // what else).
- //
- // So instead we are going to just make the call and if the result is
- // the invalid argument error, assume that the flag is not recognized.
- // Except that this error can also be returned if the link path or the
- // target path are invalid. So if we get this error, we also stat the
- // two paths to make sure we don't get the same error for them.
- //
- if (CreateSymbolicLinkA (link.string ().c_str (),
- target.string ().c_str (),
- 0x2))
- return;
+ // Try to create a symbolic link without elevated privileges by passing
+ // the new SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE flag. The flag is
+ // new and it may not be defined at compile-time so we pass its literal
+ // value.
+ //
+ // We may also be running on an earlier version of Windows (before 10
+ // build 14972) that doesn't support it. The natural way to handle that
+ // would have been to check the build of Windows that we are running on
+ // but that turns out to not be that easy (requires a deprecated API,
+ // specific executable manifest setup, a dance on one leg, and who knows
+ // what else).
+ //
+ // So instead we are going to just make the call and if the result is the
+ // invalid argument error, assume that the flag is not recognized. Except
+ // that this error can also be returned if the link path or the target
+ // path are invalid. So if we get this error, we also stat the two paths
+ // to make sure we don't get the same error for them.
+ //
+ if (CreateSymbolicLinkA (link.string ().c_str (),
+ target.string ().c_str (),
+ 0x2 | (dir ? SYMBOLIC_LINK_FLAG_DIRECTORY : 0)))
+ return;
- // Note that ERROR_INVALID_PARAMETER means that either the function
- // doesn't recognize the SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE
- // flag (that happens on elder systems) or the target or link paths are
- // invalid. Thus, we additionally check the paths to distinguish the
- // cases.
- //
- if (GetLastError () == ERROR_INVALID_PARAMETER)
+ // Note that ERROR_INVALID_PARAMETER means that either the function
+ // doesn't recognize the SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE
+ // flag (that happens on elder systems) or the target or link paths are
+ // invalid. Thus, we additionally check the paths to distinguish the
+ // cases.
+ //
+ if (GetLastError () == ERROR_INVALID_PARAMETER)
+ {
+ auto invalid = [] (const path& p)
{
- auto invalid = [] (const path& p)
- {
- return GetFileAttributesA (p.string ().c_str ()) ==
- INVALID_FILE_ATTRIBUTES &&
- GetLastError () == ERROR_INVALID_PARAMETER;
- };
+ return GetFileAttributesA (p.string ().c_str ()) ==
+ INVALID_FILE_ATTRIBUTES &&
+ GetLastError () == ERROR_INVALID_PARAMETER;
+ };
- if (invalid (target) || invalid (link))
- throw_generic_error (EINVAL);
- }
+ if (invalid (target) || invalid (link))
+ throw_generic_error (EINVAL);
+ }
+ // Fallback to creating a junction if we failed to create a directory
+ // symlink and bail out for a file symlink.
+ //
+ if (!dir)
throw_generic_error (ENOSYS, "file symlinks not supported");
- }
// Create as a junction.
//
diff --git a/libbutl/filesystem.mxx b/libbutl/filesystem.mxx
index 186c9db..5bb1ac2 100644
--- a/libbutl/filesystem.mxx
+++ b/libbutl/filesystem.mxx
@@ -248,18 +248,15 @@ LIBBUTL_MODEXPORT namespace butl
// Developer Mode enabled or if the process runs in the elevated command
// prompt.
//
- // - Directory symlinks are implemented via the Windows junction mechanism
- // that doesn't require a process to have administrative privileges and so
- // a junction can be created regardless of the Windows version and mode.
- // Note that junctions, in contrast to symlinks, may only store target
- // absolute paths. Thus, when create a directory symlink we complete its
- // target path against the current directory (unless it is already
- // absolute) and normalize.
- //
- // (@@ TODO: At some point we may want to support creating directory
- // symlinks if possible and falling back to junctions otherwise. One
- // potential issue here is with relative target paths which the caller
- // cannot rely on staying relative.)
+ // - Directory symlinks are implemented via the Windows symlink mechanism if
+ // possible (see above) and via the Windows junction mechanism otherwise.
+ // Note that creating a junction doesn't require a process to have
+ // administrative privileges and so succeeds regardless of the Windows
+ // version and mode. Also note that junctions, in contrast to symlinks,
+ // may only store target absolute paths. Thus, when create a junction we
+ // complete its target path against the current directory (unless it is
+ // already absolute) and normalize, which makes it impossible for a
+ // mksymlink() caller to rely on target path staying relative.
//
// - Functions other than mksymlink() fully support symlinks, considering
// the Windows file symlinks (file-type reparse points referring to files)