Re: [PATCH 4/5] strbuf_reset: don't write to slopbuf with ThreadSanitizer

Martin Ågren [off-list ref] writes:

quoted

diff --git a/strbuf.h b/strbuf.h
index 2075384e0b..1a77fe146a 100644
--- a/strbuf.h
+++ b/strbuf.h

@@ -147,7 +147,10 @@ static inline void strbuf_setlen(struct strbuf *sb, size_t len)
        if (len > (sb->alloc ? sb->alloc - 1 : 0))
                die("BUG: strbuf_setlen() beyond buffer");
        sb->len = len;
-       sb->buf[len] = '\0';
+       if (sb->buf != strbuf_slopbuf)
+               sb->buf[len] = '\0';
+       else
+               assert(!strbuf_slopbuf[0]);
 }

 /**

When writing my patch, I used assert() and figured that with tsan, we're
in some sort of "debug"-mode anyway. If we decide to always do the
check, would it make sense to do "else if (strbuf_slopbuf[0]) BUG(..);"
instead of the assert? Or, if we do prefer the assert, would the
performance-worry be moot?

I wasn't thinking about performance impact of having an assert();
the use of it in the above was merely copied from yours ;-)