v01d commented on issue #3157:
URL:
https://github.com/apache/incubator-nuttx/issues/3157#issuecomment-812573159
If we knew that the "important" message is emitted only in log_writev I
would simply ignore the other two and add a newline.
@donghengqaz can we assume this? This way we can also drop the unneeded
prefix.
Otherwise I think that using an internal line buffer is the only solution if
these calls will always be made separately to build the message.
Related to this discussion is the fact that I think `syslog()` should
probably handle the newline adding on its own, as per the opengroup
specification suggests (last phrase):
> The message body is generated from the message and following arguments in
the same manner as if these were arguments to printf(), except that the
additional conversion specification %m shall be recognized; it shall convert no
arguments, shall cause the output of the error message string associated with
the value of errno on entry to syslog(), and may be mixed with argument
specifications of the "%n$" form. If a complete conversion specification with
the m conversion specifier character is not just %m, the behavior is undefined.
A trailing <newline> may be added if needed.
Linux has this in its manpage:
> The remaining arguments are a format, as in printf(3), and any arguments
required by the format, except that
the two-character sequence %m will be replaced by the error message string
strerror(errno). The format string
need not include a terminating newline character.
And this is BSD:
> The message is identical to a printf(3) format string, except that `%m'
is replaced by the current error message. (As denoted by the global
variable errno; see strerror(3).) A trailing newline is added if none
is
present.
Newlines and other non-printable characters embedded in the message
string are printed in an alternate format. This prevents someone from
using non-printable characters to construct misleading log messages in
an
output file. Newlines are printed as "\n", tabs are printed as "\t".
Other control characters are printed using a caret ("^") representation,
for example "^M" for carriage return.
I think we should:
1. make syslog append newline if not present in message
2. replace other newlines with a printable character
3. Remove all use of "\n" inside syslog calls
This way we can avoid misuse of syslog()
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