Use initial working directory as process path on Linux, and expose to Lua

docs/Lua API.rst

@@ -2160,10 +2160,14 @@ unless otherwise noted.
 
   Changes the current directory to ``path``. Use with caution.
 
-* ``dfhack.filesystem.restorecwd()``
+* ``dfhack.filesystem.restore_cwd()``
 
   Restores the current working directory to what it was when DF started.
 
+* ``dfhack.filesystem.get_initial_cwd()``
+
+  Returns the value of the working directory when DF was started.
+
 * ``dfhack.filesystem.mkdir(path)``
 
   Creates a new directory. Returns ``false`` if unsuccessful, including if ``path`` already exists.

library/LuaApi.cpp

@@ -2371,7 +2371,8 @@ static const luaL_Reg dfhack_screen_funcs[] = {
 
 static const LuaWrapper::FunctionReg dfhack_filesystem_module[] = {
     WRAPM(Filesystem, getcwd),
-    WRAPM(Filesystem, restorecwd),
+    WRAPM(Filesystem, restore_cwd),
+    WRAPM(Filesystem, get_initial_cwd),
     WRAPM(Filesystem, chdir),
     WRAPM(Filesystem, mkdir),
     WRAPM(Filesystem, mkdir_recursive),

library/Process-linux.cpp

@@ -22,29 +22,28 @@ must not be misrepresented as being the original software.
 distribution.
 */
 
-#include "Internal.h"
-
+#include <cstdio>
+#include <cstring>
 #include <dirent.h>
 #include <errno.h>
+#include <map>
+#include <set>
+#include <string>
 #include <sys/mman.h>
 #include <sys/time.h>
 #include <unistd.h>
-
-#include <string>
 #include <vector>
-#include <map>
-#include <set>
-#include <cstdio>
-#include <cstring>
-using namespace std;
 
-#include <md5wrapper.h>
+#include "Error.h"
+#include "Internal.h"
+#include "md5wrapper.h"
 #include "MemAccess.h"
 #include "Memory.h"
-#include "VersionInfoFactory.h"
+#include "modules/Filesystem.h"
 #include "VersionInfo.h"
-#include "Error.h"
-#include <string.h>
+#include "VersionInfoFactory.h"
+
+using namespace std;
 using namespace DFHack;
 
 Process::Process(const VersionInfoFactory& known_versions) : identified(false), my_pe(0)
@@ -181,28 +180,7 @@ uint32_t Process::getTickCount()
 
 string Process::getPath()
 {
-    static string cached_path;
-    if (cached_path.empty())
-    {
-        const char *exe_name = "/proc/self/exe";
-        char exe_path[1024];
-        int length = readlink(exe_name, exe_path, sizeof(exe_path));
-        if (length > 0)
-        {
-            exe_path[length] = '\0';
-            string path_string = exe_path;
-            // DF lives in libs, so move up a folder
-            cached_path = path_string.substr(0, path_string.find_last_of("/", path_string.find_last_of("/") - 1));
-        }
-        else
-        {
-            perror("readlink(/proc/self/exe) failed");
-            fprintf(stderr, "  length=%i\n", length);
-            cached_path = ".";
-        }
-        fprintf(stderr, "Resolved DF root to %s\n", cached_path.c_str());
-    }
-    return cached_path;
+    return Filesystem::get_initial_cwd();
 }
 
 int Process::getPID()

library/include/modules/Filesystem.h

@@ -149,7 +149,8 @@ namespace DFHack {
         DFHACK_EXPORT void init ();
         DFHACK_EXPORT bool chdir (std::string path);
         DFHACK_EXPORT std::string getcwd ();
-        DFHACK_EXPORT bool restorecwd ();
+        DFHACK_EXPORT bool restore_cwd ();
+        DFHACK_EXPORT std::string get_initial_cwd ();
         DFHACK_EXPORT bool mkdir (std::string path);
         // returns true on success or if directory already exists
         DFHACK_EXPORT bool mkdir_recursive (std::string path);

library/modules/Filesystem.cpp

@@ -66,6 +66,7 @@ void Filesystem::init ()
 
 bool Filesystem::chdir (std::string path)
 {
+    Filesystem::init();
     return ::chdir(path.c_str()) == 0;
 }
 
@@ -83,11 +84,17 @@ std::string Filesystem::getcwd ()
     return result;
 }
 
-bool Filesystem::restorecwd ()
+bool Filesystem::restore_cwd ()
 {
     return Filesystem::chdir(initial_cwd);
 }
 
+std::string Filesystem::get_initial_cwd ()
+{
+    Filesystem::init();
+    return initial_cwd;
+}
+
 bool Filesystem::mkdir (std::string path)
 {
     int fail;