read-file.c: restore errno after successful fclose()

[eriksjolund]

Revert any change to errno from a successful fclose(). According to errno(3) a function that succeeds is allowed to change errno.

So it should be enough to

diff --git a/tools/read-file.c b/tools/read-file.c
index ee35a93..9d98663 100644
--- a/tools/read-file.c
+++ b/tools/read-file.c
@@ -118,15 +118,15 @@ char *read_file(const char *path, size_t *length)
        buf = fread_file(f, length);
 
        save_errno = errno;
 
        if (fclose(f) != 0) {
                if (buf) {
                        save_errno = errno;
                        free(buf);
                }
                errno = save_errno;
                return NULL;
        }
-
+       errno = save_errno
        return buf;
 }

I rearranged that code somewhat.

Does this PR make sense? (I'm not 100% sure)

[giuseppe]

I am not really sure why we are saving the errno in this case.

Could you just drop the saved_errno logic in this function?

[alexlarsson]

We need to save errno to ensure that if there was a read-error reading the file in fread_file() we still report that when returning a NULL buf. Otherwise fclose() may override it.