Most functions in libunwind.h are actually mapped via macros to obscure
function names, so checking for these would require some elaborate test
via AC_LINK_IFELSE(). However, unw_backtrace() seems to be one of the few
actual functions so lets use this for now, even though we don't call it
ourselves later.
Fixes: 016228c158 ("configure: Check for actual functions in libraries
with AC_CHECK_LIB")
The aikpub2 tool has been replaced by pki --pub|--req --keyid hex ..
where keyid indicates the TPM 2.0 private key object handle. Thus
either the public key in PKCS#1 format can be extracted or a PKCS#10
certificate request signed by the TPM private key can be generated.
Checking for `main` produces code like this in the test program:
int
main ()
{
return main ();
;
return 0;
}
This recursive call results in a warning message with some compilers (e.g.
Clang in newer Xcode versions: "all paths through this function will call
itself [-Winfinite-recursion]"), which lets the tests fail when compiling
with -Werror.
With AC_SEARCH_LIBS() we don't succeed if the searched function is a
built-in as the check uses the wrong signature so the built-in will not
be applied (the warning issued by GCC is "conflicting types for built-in
function '...'"). So even if not required, libatomic will be linked if
it is found, which could be problematic if compiling on a separate host
and the target host does not have libatomic installed.
Also, some tests showed that it's more likely that __atomic_and_fetch()
requires linking libatomic than __atomic_load_n() does.
References #1533.
Even if not using caching when running the configure script (-C) this
allows pre-defining the result by setting the environment variable
ss_cv_func_pthread_condattr_setclock_monotonic=yes|no|unknown
before/while running the script.
As the check requires running a test program this might be helpful
when cross-compiling to disable using monotonic time if
pthread_condattr_setclock() is defined but not actually usable with
CLOCK_MONOTONIC.
References #1502.
Tobias Brunner