builtin-clone: rewrite guess_dir_name()

diff --git a/compat/snprintf.c b/compat/snprintf.c
index dbfc2d6b6e2bc115e9976c231ae9d8fef7b2e086..580966e56a3455b9970b7eef33143c1e9c57d41c 100644 (file)
--- a/compat/snprintf.c
+++ b/compat/snprintf.c
@@ -1,12 +1,25 @@
 #include "../git-compat-util.h"
 
+/*
+ * The size parameter specifies the available space, i.e. includes
+ * the trailing NUL byte; but Windows's vsnprintf expects the
+ * number of characters to write without the trailing NUL.
+ */
+#ifndef SNPRINTF_SIZE_CORR
+#define SNPRINTF_SIZE_CORR 0
+#endif
+
 #undef vsnprintf
 int git_vsnprintf(char *str, size_t maxsize, const char *format, va_list ap)
 {
        char *s;
-       int ret;
+       int ret = -1;
 
-       ret = vsnprintf(str, maxsize, format, ap);
+       if (maxsize > 0) {
+               ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, ap);
+               /* Windows does not NUL-terminate if result fills buffer */
+               str[maxsize-1] = 0;
+       }
        if (ret != -1)
                return ret;
 
@@ -20,7 +33,7 @@ int git_vsnprintf(char *str, size_t maxsize, const char *format, va_list ap)
                if (! str)
                        break;
                s = str;
-               ret = vsnprintf(str, maxsize, format, ap);
+               ret = vsnprintf(str, maxsize-SNPRINTF_SIZE_CORR, format, ap);
        }
        free(s);
        return ret;