win32: provide a default value for HOME

The busybox-w32 shell initialises HOME when it starts.  However,
if applets are run outside the environment provided by the shell
they may find HOME is unset.  This caused a problem for 'vi' as
it was unable to locate its .exrc.

If HOME isn't available in the environment make getenv(3) provide
a sensible default value.  The shell must use the *real* getenv(3)
when determining if HOME is already set.

Also, unrelated to the above, the shell shouldn't treat failure of
getpwuid(3) as a fatal error.

Costs 72-80 bytes.

2 files changed, 19 insertions, 9 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 6a4b8e273..ebed9b50e 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -15437,6 +15437,8 @@ exitshell(void)
 }
 
 #if ENABLE_PLATFORM_MINGW32
+/* We need to see if HOME is *really* unset */
+# undef getenv
 static void xsetenv_if_unset(const char *key, const char *value)
 {
         if (!getenv(key))
@@ -15531,10 +15533,12 @@ init(void)
 
                         /* Initialise some variables normally set at login, but
                          * only if someone hasn't already set them. */
-                        pw = xgetpwuid(getuid());
-                        xsetenv_if_unset("USER",    pw->pw_name);
-                        xsetenv_if_unset("LOGNAME", pw->pw_name);
-                        xsetenv_if_unset("HOME",    pw->pw_dir);
+                        pw = getpwuid(getuid());
+                        if (pw) {
+                                xsetenv_if_unset("USER",    pw->pw_name);
+                                xsetenv_if_unset("LOGNAME", pw->pw_name);
+                                xsetenv_if_unset("HOME",    pw->pw_dir);
+                        }
                         xsetenv_if_unset("SHELL",   DEFAULT_SHELL);
                 }
 #endif
diff --git a/win32/env.c b/win32/env.c
index 8e54c4c5e..f30ee62f6 100644
--- a/win32/env.c
+++ b/win32/env.c
@@ -6,11 +6,17 @@
 char *mingw_getenv(const char *name)
 {
         char *result = getenv(name);
-        if (!result && !strcmp(name, "TMPDIR")) {
-                /* on Windows it is TMP and TEMP */
-                result = getenv("TMP");
-                if (!result)
-                        result = getenv("TEMP");
+        if (!result) {
+                if (!strcmp(name, "TMPDIR")) {
+                        /* on Windows it is TMP and TEMP */
+                        result = getenv("TMP");
+                        if (!result)
+                                result = getenv("TEMP");
+                } else if (!strcmp(name, "HOME")) {
+                        struct passwd *p = getpwuid(getuid());
+                        if (p)
+                                result = p->pw_dir;
+                }
         }
         return result;
 }