unix/main: Remove PATH_MAX from realpath.

POSIX.1-2008 ensures realpath() give a dynamically allocated buffer if
NULL is passed (which is also true for ports/windows/realpath.c),
avoiding an explicit call to malloc() and use of PATH_MAX, which may be
undefined on some systems.

Signed-off-by: David Yang <mmyangfl@gmail.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/ports/unix/main.c b/ports/unix/main.c
index 0d137fe1b..9f51573fb 100644
--- a/ports/unix/main.c
+++ b/ports/unix/main.c
@@ -453,10 +453,13 @@ static void set_sys_argv(char *argv[], int argc, int start_arg) {
 
 #if MICROPY_PY_SYS_EXECUTABLE
 extern mp_obj_str_t mp_sys_executable_obj;
-static char executable_path[MICROPY_ALLOC_PATH_MAX];
+static char *executable_path = NULL;
 
 static void sys_set_excecutable(char *argv0) {
-    if (realpath(argv0, executable_path)) {
+    if (executable_path == NULL) {
+        executable_path = realpath(argv0, NULL);
+    }
+    if (executable_path != NULL) {
         mp_obj_str_set_data(&mp_sys_executable_obj, (byte *)executable_path, strlen(executable_path));
     }
 }
@@ -721,11 +724,9 @@ MP_NOINLINE int main_(int argc, char **argv) {
                 return invalid_args();
             }
         } else {
-            char *pathbuf = malloc(PATH_MAX);
-            char *basedir = realpath(argv[a], pathbuf);
+            char *basedir = realpath(argv[a], NULL);
             if (basedir == NULL) {
                 mp_printf(&mp_stderr_print, "%s: can't open file '%s': [Errno %d] %s\n", argv[0], argv[a], errno, strerror(errno));
-                free(pathbuf);
                 // CPython exits with 2 in such case
                 ret = 2;
                 break;
@@ -734,7 +735,7 @@ MP_NOINLINE int main_(int argc, char **argv) {
             // Set base dir of the script as first entry in sys.path.
             char *p = strrchr(basedir, '/');
             mp_obj_list_store(mp_sys_path, MP_OBJ_NEW_SMALL_INT(0), mp_obj_new_str_via_qstr(basedir, p - basedir));
-            free(pathbuf);
+            free(basedir);
 
             set_sys_argv(argv, argc, a);
             ret = do_file(argv[a]);
@@ -800,6 +801,11 @@ MP_NOINLINE int main_(int argc, char **argv) {
     #endif
     #endif
 
+    #if MICROPY_PY_SYS_EXECUTABLE && !defined(NDEBUG)
+    // Again, make memory leak detector happy
+    free(executable_path);
+    #endif
+
     // printf("total bytes = %d\n", m_get_total_bytes_allocated());
     return ret & 0xff;
 }