Fix undefined behavior when getting CWD from std::filesystem

src/colvarbias_meta.cpp

@@ -11,24 +11,6 @@
 #include <iomanip>
 #include <algorithm>
 
-// Define function to get the absolute path of a replica file
-#if defined(_WIN32) && !defined(__CYGWIN__)
-#include <direct.h>
-#define GETCWD(BUF, SIZE) ::_getcwd(BUF, SIZE)
-#define PATHSEP "\\"
-#else
-#include <unistd.h>
-#define GETCWD(BUF, SIZE) ::getcwd(BUF, SIZE)
-#define PATHSEP "/"
-#endif
-
-#ifdef __cpp_lib_filesystem
-// When std::filesystem is available, use it
-#include <filesystem>
-#undef GETCWD
-#define GETCWD(BUF, SIZE) (std::filesystem::current_path().string().c_str())
-#endif
-
 #include "colvarmodule.h"
 #include "colvarproxy.h"
 #include "colvar.h"
@@ -1739,29 +1721,17 @@ int colvarbias_meta::setup_output()
 
   if (comm == multiple_replicas) {
 
-    // TODO: one may want to specify the path manually for intricated filesystems?
-    char *pwd = new char[3001];
-    if (GETCWD(pwd, 3000) == nullptr) {
-      if (pwd != nullptr) { //
-        delete[] pwd;
-      }
-      return cvm::error("Error: cannot get the path of the current working directory.\n",
-                        COLVARS_BUG_ERROR);
-    }
-
+    auto const pwd = cvm::main()->proxy->get_current_work_dir();
     replica_list_file =
-      (std::string(pwd)+std::string(PATHSEP)+
-       this->name+"."+replica_id+".files.txt");
+        cvm::main()->proxy->join_paths(pwd, this->name + "." + replica_id + ".files.txt");
     // replica_hills_file and replica_state_file are those written
     // by the current replica; within the mirror biases, they are
     // those by another replica
-    replica_hills_file =
-      (std::string(pwd)+std::string(PATHSEP)+
-       cvm::output_prefix()+".colvars."+this->name+"."+replica_id+".hills");
-    replica_state_file =
-      (std::string(pwd)+std::string(PATHSEP)+
-       cvm::output_prefix()+".colvars."+this->name+"."+replica_id+".state");
-    delete[] pwd;
+    replica_hills_file = cvm::main()->proxy->join_paths(
+        pwd, cvm::output_prefix() + ".colvars." + this->name + "." + replica_id + ".hills");
+
+    replica_state_file = cvm::main()->proxy->join_paths(
+        pwd, cvm::output_prefix() + ".colvars." + this->name + "." + replica_id + ".state");
 
     // now register this replica
 

src/colvarproxy_io.cpp

@@ -8,13 +8,20 @@
 // Colvars repository at GitHub.
 
 // Using access() to check if a file exists (until we can assume C++14/17)
-#if !defined(_WIN32) || defined(__CYGWIN__)
+#if defined(_WIN32) && !defined(__CYGWIN__)
+#include <direct.h>
+#else
 #include <unistd.h>
 #endif
+
 #if defined(_WIN32)
 #include <io.h>
 #endif
 
+#ifdef __cpp_lib_filesystem
+#include <filesystem>
+#endif
+
 #include <cerrno>
 #include <cstdio>
 
@@ -64,6 +71,54 @@ int colvarproxy_io::set_frame(long int)
 }
 
 
+std::string colvarproxy_io::get_current_work_dir() const
+{
+#ifdef __cpp_lib_filesystem
+
+  return std::filesystem::current_path().string();
+
+#else
+
+  // Legacy code
+  size_t constexpr buf_size = 3001;
+  std::string cwd;
+  char buf[buf_size];
+
+#if defined(_WIN32) && !defined(__CYGWIN__)
+  char *getcwd_result = ::_getcwd(buf, buf_size);
+#else
+  char *getcwd_result = ::getcwd(buf, buf_size);
+#endif
+
+  if (getcwd_result == nullptr) {
+    cvm::error("Error: cannot read the current working directory.\n", COLVARS_INPUT_ERROR);
+    return std::string("");
+  }
+
+  return std::string(getcwd_result);
+#endif
+}
+
+
+std::string colvarproxy_io::join_paths(std::string const &path1, std::string const &path2) const
+{
+#ifdef __cpp_lib_filesystem
+
+  return (std::filesystem::path(path1) / std::filesystem::path(path2)).string();
+
+#else
+
+  // Legacy code
+#if defined(_WIN32) && !defined(__CYGWIN__)
+  return (path1 + "\\" + path2);
+#else
+  return (path1 + "/" + path2);
+#endif
+
+#endif
+}
+
+
 int colvarproxy_io::backup_file(char const *filename)
 {
   // Simplified version of NAMD_file_exists()

src/colvarproxy_io.h

@@ -38,6 +38,12 @@ class colvarproxy_io {
   // Returns error code
   virtual int set_frame(long int);
 
+  /// Get the current working directory of this process
+  virtual std::string get_current_work_dir() const;
+
+  /// Join two paths using the operating system's path separation
+  virtual std::string join_paths(std::string const &path1, std::string const &path2) const;
+
   /// \brief Rename the given file, before overwriting it
   virtual int backup_file(char const *filename);