From 6059723900f2af1fbd394c457d1feae342e344f6 Mon Sep 17 00:00:00 2001
From: Ron Yorston <rmy@pobox.com>
Date: Thu, 13 Aug 2020 13:56:17 +0100
Subject: 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.
---
 win32/mingw.c   | 15 +++++++++++++++
 win32/process.c | 11 ++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

(limited to 'win32')

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) {
-- 
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