win32: revert special treatment of Unix-style absolute paths

Commit 605972390 (win32: handle Unix-style absolute paths for
executables) added special treatment of paths for executables
starting with a slash.  Such paths are absolute on Unix but are
relative to the current drive on Windows.  On reflection this
commit did more than necessary.  Later commits provided special
treatment only for paths starting with locations traditionally
used to contain binaries on Unix.  This is probably sufficient.

Problems introduced by commit 605972390 include:

- If the current drive isn't the system drive tab completion of a
  command starting with a slash confusingly references the system
  drive.

- Building busybox-w32 with w64devkit fails on drives other than
  the system drive.

Revert the changes introduced by commit 605972390.

This saves 192 bytes.

(GitHub issue #239)

1 files changed, 12 insertions, 33 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 8497538b1..13200da0c 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -2158,17 +2158,13 @@ maybe_single_quote(const char *s)
 }
 
 #if ENABLE_PLATFORM_MINGW32
-/*
- * Place 'path' in a string on the stack, adding the system drive prefix
- * if necessary and leaving room for an optional extension.
- */
+/* Copy path to a string on the stack long enough to allow a file extension
+ * to be added. */
 static char *
-stack_add_system_drive(const char *path)
+stack_add_ext_space(const char *path)
 {
-        const char *sd = need_system_drive(path);
-        char *p = growstackto(strlen(path) + 5 + (sd ? strlen(sd) : 0));
-
-        strcpy(stpcpy(p, sd ?: ""), path);
+        char *p = growstackto(strlen(path) + 5);
+        strcpy(p, path);
         return p;
 }
 #endif
@@ -2947,10 +2943,6 @@ padvance_magic(const char **path, const char *name, int magic)
         const char *start;
         size_t qlen;
         size_t len;
-#if ENABLE_PLATFORM_MINGW32
-        size_t sdlen = 0;
-        const char *sd;
-#endif
 
         if (*path == NULL)
                 return -1;
@@ -2982,20 +2974,11 @@ padvance_magic(const char **path, const char *name, int magic)
         *path = *p == PATH_SEP ? p + 1 : NULL;
 
         /* "2" is for '/' and '\0' */
-        qlen = len + strlen(name) + 2;
-#if ENABLE_PLATFORM_MINGW32
-        /* reserve space for system drive prefix and extension */
-        sd = need_system_drive(start);
-        if (sd != NULL)
-                sdlen = strlen(sd);
-        qlen += 4 + sdlen;
-#endif
+        /* reserve space for suffix on WIN32 */
+        qlen = len + strlen(name) + 2 IF_PLATFORM_MINGW32(+ 4);
         q = growstackto(qlen);
 
         if (len) {
-#if ENABLE_PLATFORM_MINGW32
-                q = mempcpy(q, sd, sdlen);
-#endif
                 q = mempcpy(q, start, len);
 #if ENABLE_PLATFORM_MINGW32
                 if (q[-1] != '/' && q[-1] != '\\')
@@ -9058,10 +9041,6 @@ static void shellexec(char *prog, char **argv, const char *path, int idx)
          || (applet_no = find_applet_by_name(prog)) >= 0
 #endif
         ) {
-#if ENABLE_PLATFORM_MINGW32
-                char *oldprog = prog;
-                prog = stack_add_system_drive(prog);
-#endif
                 tryexec(IF_FEATURE_SH_STANDALONE(applet_no,) prog, argv, envp);
                 if (applet_no >= 0) {
                         /* We tried execing ourself, but it didn't work.
@@ -9072,15 +9051,15 @@ static void shellexec(char *prog, char **argv, const char *path, int idx)
                 }
                 e = errno;
 #if ENABLE_PLATFORM_MINGW32
-                if (unix_path(oldprog) && !find_builtin(bb_basename(oldprog))) {
+                if (unix_path(prog) && !find_builtin(bb_basename(prog))) {
 # if ENABLE_FEATURE_SH_STANDALONE
-                        const char *name = bb_basename(oldprog);
+                        const char *name = bb_basename(prog);
                         if ((applet_no = find_applet_by_name(name)) >= 0) {
                                 tryexec(applet_no, name, argv, envp);
                                 e = errno;
                         }
 # endif
-                        argv[0] = (char *)bb_basename(oldprog);
+                        argv[0] = (char *)bb_basename(prog);
                         goto try_PATH;
                 }
 #endif
@@ -9523,7 +9502,7 @@ describe_command(char *command, const char *path, int describe_command_verbose)
 #endif
                 if (j < 0) {
 #if ENABLE_PLATFORM_MINGW32
-                        p = stack_add_system_drive(command);
+                        p = stack_add_ext_space(command);
 #else
                         p = command;
 #endif
@@ -14720,7 +14699,7 @@ find_command(char *name, struct cmdentry *entry, int act, const char *path)
         if (has_path(name)) {
                 entry->u.index = -1;
                 entry->cmdtype = CMDNORMAL;
-                fullname = stack_add_system_drive(name);
+                fullname = stack_add_ext_space(name);
                 if (add_win32_extension(fullname) || file_is_executable(fullname)) {
                         return;
                 } else if (unix_path(name) && !find_builtin(bb_basename(name))) {