use unix path format in io primitives

src/library/vm/vm_io.cpp

@@ -80,7 +80,7 @@ namespace lean {
 MK_THREAD_LOCAL_GET(std::string, local_cwd, lgetcwd())
 
 std::string abspath(std::string const & path) {
-    return normalize_path( (sstream() << local_cwd() << "/" << path).str() );
+    return (sstream() << local_cwd() << "/" << to_unix_path(path)).str();
 }
 
 optional<std::string> local_realpath(std::string const & path) {

src/util/path.cpp

@@ -121,6 +121,14 @@ std::string normalize_path(std::string f) {
     return f;
 }
 
+std::string to_unix_path(std::string f) {
+    for (auto & c : f) {
+        if (c == '\\')
+            c = '/';
+    }
+    return f;
+}
+
 std::string get_path(std::string f) {
     while (true) {
         if (f.empty())

src/util/path.h

@@ -28,6 +28,8 @@ bool is_path_sep(char c);
 
 std::string normalize_path(std::string f);
 
+std::string to_unix_path(std::string f);
+
 /** \brief Find all files with the given extension recursively. */
 void find_files(std::string const & base, char const * ext, std::vector<std::string> & files);
 bool has_file_ext(std::string const & fname, char const * ext);