win32: code shrink system drive handling

A previous commit (e3bfe3695) revised the use of getsysdir() to
obtain the system directory, and hence the system drive.  See the
commit message for the history to that point.

Further improvements are possible:

- Remove getsysdir() and push the calls to GetSystemDirectory()
  down into get_system_drive() and get_proc_addr().

- Check the return value of GetSystemDirectory().  It's unlikely
  to fail, but better safe than sorry.

- Instead of making all callers of get_system_drive() check for a
  NULL return value always return a non-NULL pointer.  If the drive
  can't be found an empty string is returned instead (which is what
  the callers were using anyway).

- The function need_system_drive() was only used in one place (in
  httpd).  Move the code there and remove the function.

- Use concat_path_file() where possible.

Saves 76-144 bytes.

5 files changed, 22 insertions, 35 deletions

diff --git a/include/mingw.h b/include/mingw.h
index 93fad0605..b0342337d 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -622,7 +622,6 @@ int enumerate_links(const char *file, char *name);
 int unc_root_len(const char *dir);
 int root_len(const char *path);
 const char *get_system_drive(void);
-const char *need_system_drive(const char *path);
 int chdir_system_drive(void);
 char *xabsolute_path(char *path);
 char *get_drive_cwd(const char *path, char *buffer, int size);
diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index 54be59f2d..97dfb3df8 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -781,7 +781,7 @@ static void install_links(const char *busybox, int use_symbolic_links,
         unsigned i;
         int rc;
 #  if ENABLE_PLATFORM_MINGW32
-        const char *sd = NULL;
+        const char *sd = "";
 
         if (custom_install_dir != NULL) {
                 bb_make_directory(custom_install_dir, 0755, FILEUTILS_RECUR);
@@ -789,7 +789,7 @@ static void install_links(const char *busybox, int use_symbolic_links,
         else {
                 sd = get_system_drive();
                 for (i=1; i<ARRAY_SIZE(install_dir); ++i) {
-                        fpc = xasprintf("%s%s", sd ?: "", install_dir[i]);
+                        fpc = concat_path_file(sd, install_dir[i]);
                         bb_make_directory(fpc, 0755, FILEUTILS_RECUR);
                         free(fpc);
                 }
@@ -802,7 +802,7 @@ static void install_links(const char *busybox, int use_symbolic_links,
 
         for (i = 0; i < ARRAY_SIZE(applet_main); i++) {
 #  if ENABLE_PLATFORM_MINGW32
-                fpc = xasprintf("%s%s/%s.exe", sd ?: "",
+                fpc = xasprintf("%s%s/%s.exe", sd,
                                 custom_install_dir ?: install_dir[APPLET_INSTALL_LOC(i)],
                                 appname);
 #  else
diff --git a/networking/httpd.c b/networking/httpd.c
index bd3a5a097..1dae602ee 100644
--- a/networking/httpd.c
+++ b/networking/httpd.c
@@ -754,10 +754,11 @@ static int parse_conf(const char *path, int flag)
                 filename = alloca(strlen(path) + sizeof(HTTPD_CONF) + 2);
                 sprintf((char *)filename, "%s/%s", path, HTTPD_CONF);
 #else
-                const char *sd = need_system_drive(path);
+                const char *sd = "";
+                if (root_len(path) == 0 && (path[0] == '/' || path[0] == '\\'))
+                        sd = get_system_drive();
 
-                filename = auto_string(xasprintf("%s%s/%s", sd ? sd : "",
-                                path, HTTPD_CONF));
+                filename = auto_string(xasprintf("%s%s/%s", sd, path, HTTPD_CONF));
 #endif
         }
 
diff --git a/shell/ash.c b/shell/ash.c
index e2dcb0962..881bc12ab 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -16292,7 +16292,7 @@ int ash_main(int argc UNUSED_PARAM, char **argv)
 
                 state = 1;
 #if ENABLE_PLATFORM_MINGW32
-                hp = xasprintf("%s/etc/profile", get_system_drive() ?: "");
+                hp = concat_path_file(get_system_drive(), "/etc/profile");
                 read_profile(hp);
                 free((void *)hp);
 #else
diff --git a/win32/mingw.c b/win32/mingw.c
index 7e42e4434..6544d11ad 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -1146,17 +1146,6 @@ static char *gethomedir(void)
         return buf;
 }
 
-static char *getsysdir(void)
-{
-        static char *buf = NULL;
-
-        if (!buf) {
-                buf = xzalloc(PATH_MAX);
-                GetSystemDirectory(buf, PATH_MAX);
-        }
-        return buf;
-}
-
 #define NAME_LEN 100
 char *get_user_name(void)
 {
@@ -2297,27 +2286,21 @@ int root_len(const char *path)
 
 const char *get_system_drive(void)
 {
-        static char *drive = NULL;
+        static const char *drive = NULL;
+        char sysdir[PATH_MAX];
         int len;
 
         if (drive == NULL) {
-                const char *sysdir = getsysdir();
-                if ((len=root_len(sysdir))) {
+                UINT ret = GetSystemDirectory(sysdir, PATH_MAX);
+                if ((ret != 0 && ret < PATH_MAX) && (len=root_len(sysdir)))
                         drive = xstrndup(sysdir, len);
-                }
+                else
+                        drive = "";
         }
 
         return getenv(BB_SYSTEMROOT) ?: 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;
-}
-
 int chdir_system_drive(void)
 {
         const char *sd = get_system_drive();
@@ -2409,10 +2392,14 @@ void *get_proc_addr(const char *dll, const char *function,
                  * on Windows 7.  If it does, retry using LoadLibrary with an
                  * explicit, backslash-separated path. */
                 if (!hnd) {
-                        char *path = concat_path_file(getsysdir(), dll);
-                        slash_to_bs(path);
-                        hnd = LoadLibrary(path);
-                        free(path);
+                        char buf[PATH_MAX];
+                        UINT ret = GetSystemDirectory(buf, PATH_MAX);
+                        if (ret != 0 && ret < PATH_MAX) {
+                                char *path = concat_path_file(buf, dll);
+                                slash_to_bs(path);
+                                hnd = LoadLibrary(path);
+                                free(path);
+                        }
                 }
 
                 if (hnd)