win32: handle Unix-style absolute paths for executables

As noted in commit 548ec7045 (win32: interpret absolute paths as
relative to %SYSTEMDRIVE%) a path starting with a '/' in the Unix
world is treated as relative to the current drive by Windows.
To avoid ambiguity that commit considered certain such paths to
be relative to %SYSTEMDRIVE%.  Extend this to paths representing
executables.

Add the functions need_system_drive() and auto_add_system_drive()
to detect the need for a system drive prefix and to add it if
necessary.  Use these functions in:

- the 'which' applet
- the find_executable() function
- tab-completion code
- PATH look-up, shellexec(), describe_command() and find_command() in ash
- parse_interpreter() and mingw_spawn_1()

With these changes executable paths starting with a slash are
handled consistently, whatever the current drive.

2 files changed, 25 insertions, 1 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index 8501ecdd4..e63ffa0ac 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -1698,6 +1698,21 @@ const char *get_system_drive(void)
         return drive;
 }
 
+/* Return pointer to system drive if path is of form '/file', else NULL */
+const char *need_system_drive(const char *path)
+{
+        if (root_len(path) == 0 && (path[0] == '/' || path[0] == '\\'))
+                return get_system_drive();
+        return NULL;
+}
+
+/* Add a system drive prefix to 'path' if necessary, else return 'path' */
+char *auto_add_system_drive(const char *path)
+{
+        const char *sd = need_system_drive(path);
+        return sd ? auto_string(concat_path_file(sd, path)) : (char *)path;
+}
+
 int chdir_system_drive(void)
 {
         const char *sd = get_system_drive();
diff --git a/win32/process.c b/win32/process.c
index 1118eb18a..cd164e0ed 100644
--- a/win32/process.c
+++ b/win32/process.c
@@ -63,6 +63,7 @@ static int
 parse_interpreter(const char *cmd, interp_t *interp)
 {
         char *path, *t;
+        const char *sd;
         int n;
 
         while (TRUE) {
@@ -88,6 +89,12 @@ parse_interpreter(const char *cmd, interp_t *interp)
                 if (*t == '\0')
                         break;
 
+                sd = need_system_drive(path);
+                if (sd && strlen(sd) == 2) {
+                        path -= 2;
+                        memcpy(path, sd, 2);
+                }
+
                 interp->path = path;
                 interp->name = t;
                 interp->opts = strtok(NULL, "\r\n");
@@ -342,6 +349,7 @@ static intptr_t
 mingw_spawn_1(int mode, const char *cmd, char *const *argv, char *const *envp)
 {
         char *prog;
+        const char *path;
 
 #if ENABLE_FEATURE_PREFER_APPLETS || ENABLE_FEATURE_SH_STANDALONE
         if (find_applet_by_name(cmd) >= 0)
@@ -349,7 +357,8 @@ mingw_spawn_1(int mode, const char *cmd, char *const *argv, char *const *envp)
         else
 #endif
         if (has_path(cmd)) {
-                const char *path = auto_win32_extension(cmd);
+                cmd = auto_add_system_drive(cmd);
+                path = auto_win32_extension(cmd);
                 return mingw_spawn_interpreter(mode, path ? path : cmd, argv, envp, 0);
         }
         else if ((prog=find_first_executable(cmd)) != NULL) {