avoid the thread-ptr-init behavior of sigaction when not installing handler

this is necessary because posix_spawn calls sigaction after vfork, and
if the thread pointer is not already initialized, initializing it in
the child corrupts the parent process's state.

diff --git a/src/signal/sigaction.c b/src/signal/sigaction.c
index 2331dc9..d953503 100644 (file)
--- a/src/signal/sigaction.c
+++ b/src/signal/sigaction.c
@@ -15,12 +15,13 @@ int __libc_sigaction(int sig, const struct sigaction *restrict sa, struct sigact
 {
        struct k_sigaction ksa;
        if (sa) {
+               if ((uintptr_t)sa->sa_handler > 1UL)
+                       __pthread_self_def();
                ksa.handler = sa->sa_handler;
                ksa.flags = sa->sa_flags | SA_RESTORER;
                ksa.restorer = (sa->sa_flags & SA_SIGINFO) ? __restore_rt : __restore;
                memcpy(&ksa.mask, &sa->sa_mask, sizeof ksa.mask);
        }
-       __pthread_self_def();
        if (syscall(SYS_rt_sigaction, sig, sa?&ksa:0, old?&ksa:0, sizeof ksa.mask))
                return -1;
        if (old) {