win32: fix clang error/warning

Since clang doesn't seem to know about ffs(3) make it use
__builtin_ffs() instead.

Fix a warning in process_escape() in winansi.c:  result of comparison
of constant -1 with expression of type 'WORD' (aka 'unsigned short')
is always true.  Change the error value returned by process_colour()
from -1 to 0xffff.

Costs 16 bytes.

2 files changed, 7 insertions, 3 deletions

diff --git a/include/mingw.h b/include/mingw.h
index 88da85243..4abdcf459 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -236,7 +236,11 @@ int strverscmp(const char *s1, const char *s2);
 /*
  * strings.h
  */
+#if !defined(__clang__)
 int ffs(int i);
+#else
+# define ffs(i) __builtin_ffs(i)
+#endif
 
 /*
  * sys/ioctl.h
diff --git a/win32/winansi.c b/win32/winansi.c
index ff4f4b118..6142a244c 100644
--- a/win32/winansi.c
+++ b/win32/winansi.c
@@ -518,7 +518,7 @@ static char *process_colour(char *str, WORD *attr)
 {
         long val = strtol(str, (char **)&str, 10);
 
-        *attr = -1;     /* error return */
+        *attr = 0xffff; /* error return */
         switch (val) {
         case 2:
                 str = process_24bit(str + 1, attr);
@@ -628,7 +628,7 @@ static char *process_escape(char *pos)
                                 break;
                         case 38: /* 8/24 bit */
                                 str = process_colour(str + 1, &t);
-                                if (t != -1) {
+                                if (t != 0xffff) {
                                         attr &= ~(FOREGROUND_ALL|FOREGROUND_INTENSITY);
                                         attr |= t;
                                 }
@@ -652,7 +652,7 @@ static char *process_escape(char *pos)
                                 break;
                         case 48: /* 8/24 bit */
                                 str = process_colour(str + 1, &t);
-                                if (t != -1) {
+                                if (t != 0xffff) {
                                         attr &= ~(BACKGROUND_ALL|BACKGROUND_INTENSITY);
                                         attr |= t << 4;
                                 }