Re: [PATCH 1/5] Make xstrndup common

On Apr 29, 2007, at 1:29 PM, Josh Triplett wrote:

Daniel Barkalow wrote:

quoted

On Sat, 28 Apr 2007, Josh Triplett wrote:

quoted

Daniel Barkalow wrote:

quoted

It was implemented in commit.c; move it with the other x memory  
functions.

[...]

quoted

+static inline char *xstrndup(const char *str, int len)
+{
+	char *ret = xmalloc(len + 1);
+	memcpy(ret, str, len);
+	ret[len] = '\0';
+	return ret;
+}
+

I don't know if it matters, but this definition of xstrndup, like  
the version
in commit.c, doesn't match the definition of strndup.  strndup  
duplicates a
string, copying up to n characters or the length of the string.   
This xstrndup
always copies n characters, reading past the end of the string if  
it doesn't
have at least n characters.

Good catch. Replacing the memcpy with strncpy solves this, right?
(Potentially allocating a bit of extra memory if someone is  
actually using
it on too short a string for some reason, of course).

That would work, but it seems bad to allocate excess memory.  How  
about just
using strlen and setting len to that if shorter, before doing the  
xmalloc and
memcpy?  Yes, that makes two passes over the string, but I don't  
see any way
around that.

    An easy way around that is to do the string copy yourself,  
walking the string until you either find '\0' or reach len copied  
characters.

-Adam