Create file or directory before calling tmp::path constructor

include/tmp/directory.hpp

@@ -44,7 +44,7 @@ class directory final : public path {
     /// for temporary files. If a prefix is provided to the constructor, the
     /// directory is created in the path <temp dir>/prefix/. The prefix can be
     /// a path consisting of multiple segments.
-    explicit directory(std::string_view prefix = "") : path(prefix, creator) {}
+    explicit directory(std::string_view prefix = "") : path(create(prefix)) {}
 
     /// Concatenates this directory path with a given @p source
     std::filesystem::path operator/(std::string_view source) const {
@@ -60,9 +60,12 @@ class directory final : public path {
     auto operator=(const directory&) = delete;               ///< not copy-assignable
 
 private:
-    /// Creates a unique temporary directory based on the given @p pattern path.
-    /// The parent path of the given argument must exist.
-    static std::string creator(std::string pattern) {
+    /// Creates a unique temporary directory based on the given @p prefix
+    static std::filesystem::path create(std::string_view prefix) {
+        const auto parent = std::filesystem::temp_directory_path() / prefix;
+        std::filesystem::create_directories(parent);
+
+        auto pattern = std::string(parent / "XXXXXX");
         if (mkdtemp(pattern.data()) == nullptr) {
             auto ec = std::error_code(errno, std::system_category());
             throw error("Cannot create temporary directory", ec);

include/tmp/file.hpp

@@ -86,18 +86,21 @@ class file final : public path {
     /// for temporary files. If a prefix is provided to the constructor, the
     /// directory is created in the path <temp dir>/prefix/. The prefix can be
     /// a path consisting of multiple segments.
-    explicit file(std::string_view prefix, bool binary) : path(prefix, creator),
+    explicit file(std::string_view prefix, bool binary) : path(create(prefix)),
                                                           binary(binary) {}
 
-    /// Creates a unique temporary file based on the given @p pattern path.
-    /// The parent path of the given argument must exist.
-    static std::string creator(std::string path) {
-        if (mkstemp(path.data()) == -1) {
+    /// Creates a unique temporary file based on the given @p prefix
+    static std::filesystem::path create(std::string_view prefix) {
+        const auto parent = std::filesystem::temp_directory_path() / prefix;
+        std::filesystem::create_directories(parent);
+
+        auto pattern = std::string(parent / "XXXXXX");
+        if (mkstemp(pattern.data()) == -1) {
             auto ec = std::error_code(errno, std::system_category());
             throw error("Cannot create temporary file", ec);
         }
 
-        return path;
+        return pattern;
     }
 
     /// Returns a stream for this file

include/tmp/path.hpp

@@ -52,12 +52,7 @@ class path {
     /// Creates a unique temporary path using the given constructor function.
     /// @param prefix the path between system temp
     /// @param creator wrapped mktemp-like function that returns resulting path
-    explicit path(std::string_view prefix, std::string(*creator)(std::string)) {
-        const auto parent = std::filesystem::temp_directory_path() / prefix;
-        std::filesystem::create_directories(parent);
-
-        this->underlying = creator(parent / "XXXXXX");
-    }
+    explicit path(std::filesystem::path path) : underlying(path){}
 
 private:
     /// Deletes this path recursively, ignoring any errors