Due to Android (and apparently Sun) not supporting getcwd(NULL, 0), I've changed to call to getcwd to specify a buffer and explicit size which successfully works around the problem. One minor performance advantage is that one less malloc/free is needed since the buffer is now created on the stack. Apparently, this was already changed in a prior commit I didn't see initially, but I think the use of an invented/arbitrary PATH_MAX is incorrect. Platforms should generally provide a constant for this and PATH_MAX itself is already defined on some systems like Linux which can cause collisions. This commit improves on those changes by leveraging the constants provided by the compiler/system.

To help keep the code consistent but still correct, new platform specific code needed to be introduced for the max length. On POSIX I am assuming it is that <sys/param.h> provides MAXPATHLEN. This is what the Mac/BSD man page says to use and verified this is also defined on Ubuntu Linux and Android. On Windows, MAX_PATH is used. MAX_PATH seems to still be 260 which seems kind of small; is there a different constant we are supposed to use? In both cases, the respective constants are mapped to a new #define for LFS_MAXPATHLEN to allow the code to refer to one constant and avoid any potential name collisions in case MAXPATHLEN is defined already by something else on Windows (e.g. Cygwin).

1 files changed, 10 insertions, 6 deletions

diff --git a/src/lfs.c b/src/lfs.c
index a784d77..f3a6ce8 100644
--- a/src/lfs.c
+++ b/src/lfs.c
@@ -82,6 +82,12 @@
 #define getcwd_error    "Function 'getcwd' not provided by system"
 #else
 #define getcwd_error    strerror(errno)
+  #ifdef _WIN32
+    #define LFS_MAXPATHLEN MAX_PATH // MAX_PATH seems to be 260. Seems kind of small. Is there a better one?
+  #else
+    #include <sys/param.h> // for MAXPATHLEN
+    #define LFS_MAXPATHLEN MAXPATHLEN
+  #endif
 #endif
 
 #define DIR_METATABLE "directory metatable"
@@ -160,13 +166,11 @@ static int change_dir (lua_State *L) {
 ** If unable to get the current directory, it returns nil
 **  and a string describing the error
 */
-#ifndef PATH_MAX
-#define PATH_MAX 4096
-#endif
-
 static int get_dir (lua_State *L) {
-  char path[PATH_MAX];
-  if (getcwd((char *)path, PATH_MAX) == NULL) {
+  char *path;
+  // Passing (NULL, 0) is not guaranteed to work. Use a temp buffer and size instead.
+  char buf[LFS_MAXPATHLEN]; 
+  if ((path = getcwd(buf, LFS_MAXPATHLEN)) == NULL) {
     lua_pushnil(L);
     lua_pushstring(L, getcwd_error);
     return 2;