From Cppcheck:
Passing NULL after the last typed argument to a variadic function leads to
undefined behaviour. The C99 standard, in section 7.15.1.1, states that if the
type used by va_arg() is not compatible with the type of the actual next
argument (as promoted according to the default argument promotions), the
behavior is undefined. The value of the NULL macro is an implementation-defined
null pointer constant (7.17), which can be any integer constant expression with
the value 0, or such an expression casted to (void*) (6.3.2.3). This includes
values like 0, 0L, or even 0LL.In practice on common architectures, this will
cause real crashes if sizeof(int) != sizeof(void*), and NULL is defined to 0 or
any other null pointer constant that promotes to int. To reproduce you might be
able to use this little code example on 64bit platforms. If the output includes
"ERROR", the sentinel had only 4 out of 8 bytes initialized to zero and was not
detected as the final argument to stop argument processing via
va_arg(). Changing the 0 to (void*)0 or 0L will make the "ERROR" output go away.
void f(char *s, ...) {
va_list ap;
va_start(ap,s);
for (;;) {
char *p = va_arg(ap,char*);
printf("%018p, %s\n", p, (long)p & 255 ? p : "");
if(!p) break;
}
va_end(ap);
}
void g() {
char *s2 = "x";
char *s3 = "ERROR";
// changing 0 to 0L for the 7th argument (which is intended to act as
// sentinel) makes the error go away on x86_64
f("first", s2, s2, s2, s2, s2, 0, s3, (char*)0);
}
void h() {
int i;
volatile unsigned char a[1000];
for (i = 0; i<sizeof(a); i++)
a[i] = -1;
}
int main() {
h();
g();
return 0;
}
The coccinellery repository provides many little semantic patches to fix common
problems in the code. The number of semantic patches in the coccinellery
repository is high and most of the semantic patches apply only for Linux, so it
doesn't make sense to run them on regular basis as the processing takes a lot of
time.
The list of issue found in BIND 9, by no means complete, includes:
- double assignment to a variable
- `continue` at the end of the loop
- double checks for `NULL`
- useless checks for `NULL` (cannot be `NULL`, because of earlier return)
- using `0` instead of `NULL`
- useless extra condition (`if (foo) return; if (!foo) { ...; }`)
- removing & in front of static functions passed as arguments
The dns_name_copy() function followed two different semanitcs that was driven
whether the last argument was or wasn't NULL. This commit splits the function
in two where now third argument to dns_name_copy() can't be NULL and
dns_name_copynf() doesn't have third argument.
This commit was done by hand to add the RUNTIME_CHECK() around stray
dns_name_copy() calls with NULL as third argument. This covers the edge cases
that doesn't make sense to write a semantic patch since the usage pattern was
unique or almost unique.
This second commit uses second semantic patch to replace the calls to
dns_name_copy() with NULL as third argument where the result was stored in a
isc_result_t variable. As the dns_name_copy(..., NULL) cannot fail gracefully
when the third argument is NULL, it was just a bunch of dead code.
Couple of manual tweaks (removing dead labels and unused variables) were
manually applied on top of the semantic patch.
This commit add RUNTIME_CHECK() around all simple dns_name_copy() calls where
the third argument is NULL using the semantic patch from the previous commit.
Until now, the build process for BIND on Windows involved upgrading the
solution file to the version of Visual Studio used on the build host.
Unfortunately, the executable used for that (devenv.exe) is not part of
Visual Studio Build Tools and thus there is no clean way to make that
executable part of a Windows Server container.
Luckily, the solution upgrade process boils down to just adding XML tags
to Visual Studio project files and modifying certain XML attributes - in
files which we pregenerate anyway using win32utils/Configure. Thus,
extend win32utils/Configure with three new command line parameters that
enable it to mimic what "devenv.exe bind9.sln /upgrade" does. This
makes the devenv.exe build step redundant and thus facilitates building
BIND in Windows Server containers.
The isc_refcount_decrement() was either used as:
if (isc_refcount_decrement() == 1) { destroy(); }
or
if (isc_refcount_decrement() != 1) { return; } destroy();
This commits eradicates the last usage of the later, so the code is unified to
use the former.
Currently, the lib/dns/tests/tkey_test unit test is only run when the
linker supports the --wrap option. However, linker support for that
option is only needed for static builds. As a result, the unit test
mentioned before is not being run everywhere it can be run as even for
builds done using --with-libtool, the test is not run unless the linker
supports the --wrap option.
Tweak preprocessor directives in lib/dns/tests/tkey_test.c so that this
test is run:
- for all builds using --with-libtool,
- for static builds done using a linker supporting the --wrap option.
Weak symbols are handled differently by different dynamic linkers. With
glibc, lib/dns/tests/tkey_test works as expected no matter whether
--with-libtool is used or not: __attribute__((weak)) prevents a static
build from failing and it just so happens that the desired symbols are
picked at runtime for dynamic builds. However, with BSD libc, the
libdns functions called from lib/dns/tests/tkey_test.c use the "real"
memory allocation functions from libisc, thus breaking that unit test.
(Note: similar behavior can be reproduced with glibc by setting the
LD_DYNAMIC_WEAK environment variable.)
The simplest way to make lib/dns/tests/tkey_test work reliably is to
drop all uses of __attribute__((weak)) in it - this way, the memory
functions inside lib/dns/tests/tkey_test.c will always be used instead
of the "real" libisc ones for dynamic builds. However, this would not
work with static builds as it would result in multiple strong symbols
with the same name being present in a single binary.
Work around the problem by only compiling in the overriding definitions
of memory functions when building using --with-libtool. For static
builds, keep relying on the --wrap linker option for replacing calls to
the functions we are interested in.
isc_event_allocate() calls isc_mem_get() to allocate the event structure. As
isc_mem_get() cannot fail softly (e.g. it never returns NULL), the
isc_event_allocate() cannot return NULL, hence we remove the (ret == NULL)
handling blocks using the semantic patch from the previous commit.
when looking for a possible wildcard match in the RPZ summary database,
use an rbtnodechain to walk up label by label, rather than using the
node's parent pointer.
