win32: don't test DLLs for executable format

Moving detection of file formats from access(2) to stat(2) in
commit 650f67507 was acknowledged to slow down stat.  One
problematic case is c:/windows/system32 which contains about
2000 DLLs and was found to slow 'ls' unacceptably.

Treat DLLs as a special case in has_exec_format.

See GitHub issue #101.

1 files changed, 5 insertions, 0 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index 112b2a54e..9978baa7a 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -330,6 +330,11 @@ static int has_exec_format(const char *name)
         unsigned int offset;
         unsigned char buf[1024];
 
+        /* special case: skip DLLs, there are thousands of them! */
+        n = strlen(name);
+        if (n > 4 && !strcasecmp(name+n-4, ".dll"))
+                return 0;
+
         fd = open(name, O_RDONLY);
         if (fd < 0)
                 return 0;