winansi: check for broken pipe

Microsoft Windows doesn't support SIGPIPE and its support for the
EPIPE error is somewhat inadequate.  Most of the time a broken pipe
leads to an EINVAL error which is misleading:

   $ yes hello | head -1
   hello
   yes: Invalid argument

Add a function to test for the underlying Windows error that indicates
a broken pipe and set errno to EPIPE.  Call this function in a few
strategic places.

1 files changed, 29 insertions, 6 deletions

diff --git a/win32/winansi.c b/win32/winansi.c
index 8e583e0ce..256ef4fa9 100644
--- a/win32/winansi.c
+++ b/win32/winansi.c
@@ -475,16 +475,31 @@ int winansi_puts(const char *s)
         return (winansi_fputs(s, stdout) == EOF || putchar('\n') == EOF) ? EOF : 0;
 }
 
+static void check_pipe(FILE *stream)
+{
+        if (GetLastError() == ERROR_NO_DATA && ferror(stream)) {
+                int fd = fileno(stream);
+                if (fd != -1 &&
+                                GetFileType((HANDLE)_get_osfhandle(fd)) == FILE_TYPE_PIPE) {
+                        errno = EPIPE;
+                }
+        }
+}
+
 size_t winansi_fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream)
 {
-        size_t lsize, lmemb;
+        size_t lsize, lmemb, ret;
         char *str;
         int rv;
 
         lsize = MIN(size, nmemb);
         lmemb = MAX(size, nmemb);
-        if (lsize != 1 || !is_console(fileno(stream)))
-                return fwrite(ptr, size, nmemb, stream);
+        if (lsize != 1 || !is_console(fileno(stream))) {
+                SetLastError(0);
+                if ((ret=fwrite(ptr, size, nmemb, stream)) < nmemb)
+                        check_pipe(stream);
+                return ret;
+        }
 
         str = xmalloc(lmemb+1);
         memcpy(str, ptr, lmemb);
@@ -498,8 +513,14 @@ size_t winansi_fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream)
 
 int winansi_fputs(const char *str, FILE *stream)
 {
-        if (!is_console(fileno(stream)))
-                return fputs(str, stream);
+        int ret;
+
+        if (!is_console(fileno(stream))) {
+                SetLastError(0);
+                if ((ret=fputs(str, stream)) == EOF)
+                        check_pipe(stream);
+                return ret;
+        }
 
         return ansi_emulate(str, stream) == EOF ? EOF : 0;
 }
@@ -538,7 +559,9 @@ int winansi_vfprintf(FILE *stream, const char *format, va_list list)
         return rv;
 
 abort:
-        rv = vfprintf(stream, format, list);
+        SetLastError(0);
+        if ((rv=vfprintf(stream, format, list)) == EOF)
+                check_pipe(stream);
         return rv;
 }