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Re: [Qemu-trivial] [Qemu-devel] [PATCH v2 4/5] linux-user/uname: Fix GCC
From: |
Eric Blake |
Subject: |
Re: [Qemu-trivial] [Qemu-devel] [PATCH v2 4/5] linux-user/uname: Fix GCC 9 build warnings |
Date: |
Wed, 1 May 2019 07:00:03 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 |
On 5/1/19 4:40 AM, Laurent Vivier wrote:
> On 01/05/2019 01:28, Alistair Francis wrote:
>> Fix this warning when building with GCC9 on Fedora 30:
>> In function ‘strncpy’,
>> inlined from ‘sys_uname’ at /home/alistair/qemu/linux-user/uname.c:94:3:
>> /usr/include/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’
>> output may be truncated copying 64 bytes from a string of length 64
>> [-Werror=stringop-truncation]
>> 106 | return __builtin___strncpy_chk (__dest, __src, __len, __bos
>> (__dest));
>> |
>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> Signed-off-by: Alistair Francis <address@hidden>
>> ---
>> linux-user/uname.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/linux-user/uname.c b/linux-user/uname.c
>> index 313b79dbad..2fc6096a5b 100644
>> --- a/linux-user/uname.c
>> +++ b/linux-user/uname.c
>> @@ -73,7 +73,7 @@ const char *cpu_to_uname_machine(void *cpu_env)
>> #define COPY_UTSNAME_FIELD(dest, src) \
>> do { \
>> /* __NEW_UTS_LEN doesn't include terminating null */ \
>> - (void) strncpy((dest), (src), __NEW_UTS_LEN); \
>> + (void) memcpy((dest), (src), MIN(strlen(src), __NEW_UTS_LEN)); \
>
> You should use MIN(strlen(src) + 1, __NEW_UTS_LEN) to copy the NUL
> character if it is present and fit in __NEW_UTS_LEN.
No, the NUL character is already present, due to the memset() prior to
any use of COPY_UTSNAME_FIELD(). However, the commit message should
call that out, as it is not part of the default 3-line diff.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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