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MDEV-22387: Static_binary_string::q_append() invokes memcpy on NULL

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Invoking memcpy() on a NULL pointer is undefined behaviour
(even if the length is 0) and gives the compiler permission to
assume that the pointer is nonnull. Recent versions of GCC
(starting with version 8) are more aggressively optimizing away
checks for NULL pointers. This undefined behaviour would cause
a SIGSEGV in the test main.func_encrypt on an optimized debug build
on GCC 10.2.0.
This commit is contained in:
Marko Mäkelä 2020-10-30 13:07:42 +02:00
parent 199863d72b
commit cb253b8687
1 changed files with 2 additions and 1 deletions
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3
sql/sql_string.h
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@ -313,7 +313,8 @@ public:
}
void q_append(const char *data, size_t data_len)
{
memcpy(Ptr + str_length, data, data_len);
if (data_len)
memcpy(Ptr + str_length, data, data_len);
DBUG_ASSERT(str_length <= UINT_MAX32 - data_len);
str_length += (uint)data_len;
}