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

From: Torsten Bögershausen <[email-masked]>
Date: Sun, 27 Sep 2015 15:06:44 +0200

On 2015-09-27 13.19, René Scharfe wrote:
> Am 24.09.2015 um 23:08 schrieb Jeff King:
>> 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 <[email-masked]>
>> ---
>>   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 ?)