[systemd-devel] [PATCH 2/2] journal: get rid of LINE_MAX in sd_journal_printv*()

[Zbigniew Jędrzejewski-Szmek]

On Mon, Apr 15, 2013 at 10:17:45PM +0200, Harald Hoyer wrote:
> Am 15.04.2013 21:29, schrieb Zbigniew Jędrzejewski-Szmek:
> > On Mon, Apr 15, 2013 at 06:41:52PM +0200, harald at redhat.com wrote:
> >> From: Harald Hoyer <harald at redhat.com>
> >>
> >> use stack_size_guess() to get rid of LINE_MAX
> >> ---
> >>  src/journal/journal-send.c      | 99 +++++++++++++++++++++++++++++++----------
> >>  src/journal/test-journal-send.c | 92 +++++++++++++++++++++++++++++++++-----
> >>  2 files changed, 156 insertions(+), 35 deletions(-)
> >>
> >> diff --git a/src/journal/journal-send.c b/src/journal/journal-send.c
> >> index 4b9109a..2ff04b4 100644
> >> --- a/src/journal/journal-send.c
> >> +++ b/src/journal/journal-send.c
> >> @@ -26,6 +26,7 @@
> >>  #include <unistd.h>
> >>  #include <fcntl.h>
> >>  #include <printf.h>
> >> +#include <sys/resource.h>
> >>  
> >>  #define SD_JOURNAL_SUPPRESS_LOCATION
> >>  
> >> @@ -35,15 +36,17 @@
> >>  
> >>  #define SNDBUF_SIZE (8*1024*1024)
> >>  
> >> -#define ALLOCA_CODE_FUNC(f, func)                 \
> >> -        do {                                      \
> >> -                size_t _fl;                       \
> >> -                const char *_func = (func);       \
> >> -                char **_f = &(f);                 \
> >> -                _fl = strlen(_func) + 1;          \
> >> -                *_f = alloca(_fl + 10);           \
> >> -                memcpy(*_f, "CODE_FUNC=", 10);    \
> >> -                memcpy(*_f + 10, _func, _fl);     \
> >> +#define ALLOCA_CODE_FUNC(f, func)                    \
> >> +        do {                                         \
> >> +                size_t _fl;                          \
> >> +                const char *_func = (func);          \
> >> +                char **_f = &(f);                    \
> >> +                _fl = strlen(_func) + 1;             \
> >> +                if (stack_size_guess() < (_fl + 10)) \
> > Can't _fl + 10 overflow (on 32 bit)?
> 
> You mean signed vs unsigned?
No, I mean _fl can be 4×2³² - 9, and, then _fl+10 == 1.
C99 says size_t is "at least 16 bits", although I don't
think that less than 32 bits is common.
On a modern machine strlen() on a 4GB string should take
about a second, so it seems plausible to feed this function
with a big enough string, maybe on a kernel with PAE.

Zbyszek