Re: [PATCH 60/68] prefer memcpy to strcpy

Am 27.09.2015 um 15:13 schrieb René Scharfe:

Am 27.09.2015 um 15:06 schrieb Torsten Bögershausen:

quoted

On 2015-09-27 13.19, René Scharfe wrote:

quoted

Am 24.09.2015 um 23:08 schrieb Jeff King:

quoted

When we already know the length of a string (e.g., because
we just malloc'd to fit it), it's nicer to use memcpy than
strcpy, as it makes it more obvious that we are not going to
overflow the buffer (because the size we pass matches the
size in the allocation).

This also eliminates calls to strcpy, which make auditing
the code base harder.

Signed-off-by: Jeff King <redacted>
---
   compat/nedmalloc/nedmalloc.c | 5 +++--
   fast-import.c                | 5 +++--
   revision.c                   | 2 +-
   3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/compat/nedmalloc/nedmalloc.c

b/compat/nedmalloc/nedmalloc.c
index 609ebba..a0a16eb 100644

--- a/compat/nedmalloc/nedmalloc.c
+++ b/compat/nedmalloc/nedmalloc.c

@@ -957,8 +957,9 @@ char *strdup(const char *s1)
   {
       char *s2 = 0;
       if (s1) {
-        s2 = malloc(strlen(s1) + 1);
-        strcpy(s2, s1);
+        size_t len = strlen(s1) + 1;
+        s2 = malloc(len);
+        memcpy(s2, s1, len);

This leaves the last byte uninitialized; it was set to NUL by
strcpy() before.

len is == strlen() +1, which should cover the NUL:

1 byte extra for NUL is allocated,
and memcpy will copy NUL from source.
(Or do I miss somethong ?)

No, you're right.  Sorry for the noise.

I fully blame this on lack of coffeine because my electric kettle just
broke. O_o

Thinking a bit more about it (slowly): The choice of the variable name 
might have been a factor as well.  When I see "len" for a string then I 
don't expect it to include the trailing NUL.  "size" would be better 
because I expect it to contain the number of bytes needed to store an 
object.

René