Add memcpy_safe

ISO/IEC 9899:1999 §7.21.1/2 says:
Where an argument declared as size_t n specifies the length of the array
for a function, n can have the value zero on a call to that
function. Unless explicitly stated otherwise in the description of a
particular function in this subclause, pointer arguments on such a call
shall still have valid values, as described in 7.1.4.

In base64_append_width memcpy was called as memcpy(x, NULL, 0).  GCC 4.9
started making use of this and assumes This worked fine under -O0, but
does something strange under -O3.

This patch fixes a bug in base64_append_width(), fixes a possible bug in
journal_file_append_entry_internal(), and makes use of the new function
to simplify the code in other places.

1 files changed, 3 insertions, 8 deletions

diff --git a/src/libsystemd-network/test-dhcp-option.c b/src/libsystemd-network/test-dhcp-option.c
index 7b80a5bd90..45f4e0b5f5 100644
--- a/src/libsystemd-network/test-dhcp-option.c
+++ b/src/libsystemd-network/test-dhcp-option.c
@@ -112,14 +112,9 @@ static DHCPMessage *create_message(uint8_t *options, uint16_t optlen,
         message = malloc0(len);
         assert_se(message);
 
-        if (options && optlen)
-                memcpy(&message->options, options, optlen);
-
-        if (file && filelen <= 128)
-                memcpy(&message->file, file, filelen);
-
-        if (sname && snamelen <= 64)
-                memcpy(&message->sname, sname, snamelen);
+        memcpy_safe(&message->options, options, optlen);
+        memcpy_safe(&message->file, file, filelen);
+        memcpy_safe(&message->sname, sname, snamelen);
 
         return message;
 }