Hello tianye,
On 12/20/22 03:59, tia...@sugon.com wrote:
Hi:
I have a testcode, it will lead to uart print space forever.
Demo code like this:
Init()
{
create a task;
start this task;
*printf("%*\n");* while(1) { sleep() } } This code lead to uart print
space forever('SPACE' ascii is 0x20):
'SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE''SPACE'......
"%*\n" is an illegal or incorrect "conversion specification" because is
misses an "conversion specifier" (e.g. an "d", "s" or "x" before the
"\n"). Whether the behavior is a bug depends on the specification of the
behavior of `printf()` in such a case. I am not aware of any
specification of what should happen when the "conversion specification"
is malformed.
I tried with gcc on an ordinary Linux and it printed (to my surprise):
%107348472
The print out of spaces cannot be excused with the presents of a field
with specifier "*" because without knowing the length of the content of
the field - due to the missing conversion specifier - the software
cannot calculate how may spaces to print out.
Anyway, your `printf()` should trigger this compiler warning:
../../../testsuites/samples/hello/init.c:44:14: warning: unknown
conversion type character '\x0a' in format [-Wformat=]
44 | printf( "%*\n" );
| ^~
Since the issue appears to be triggered in newlib code, I believe
changing RTEMS code wont help in any case. Yet, again it is dubious to
me whether this is a bug in the first place.
Greetings
Frank
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