patch libedit to stop re-broadcasting signals

Author: oconnor663

cpython-unix/build-libedit.sh

@@ -82,6 +82,32 @@ index 614795f..4671f1b 100755
  fi
 EOF
 
+# When libedit receives a signal, it re-broadcasts it to its entire pgroup.
+# This seems intended to preserve normal ^C behavior in "raw" mode when the
+# terminal's ISIG flag is cleared? However, libedit does not in fact clear
+# ISIG. (And Jack can't find any evidence of any version that ever did.) This
+# sometimes results in the parent process receiving ^C twice back-to-back,
+# depending on the vagaries of signal coalescing. More pathologically, if the
+# parent tries to signal the child directly with e.g. `kill(pid, SIGTERM)`,
+# libedit *signals the parent right back* (not to mention any other pgroup
+# siblings or grandparents). This is just wild behavior, even though it's
+# probably rare that it matters in practice. Patch it out. See also:
+# https://github.com/astral-sh/uv/issues/13919#issuecomment-2960501229.
+patch -p1 << "EOF"
+diff --git i/src/sig.c w/src/sig.c
+index d2b77e7..884b2dd 100644
+--- i/src/sig.c
++++ w/src/sig.c
+@@ -107,7 +107,7 @@ sig_handler(int signo)
+ 	sel->el_signal->sig_action[i].sa_flags = 0;
+ 	sigemptyset(&sel->el_signal->sig_action[i].sa_mask);
+ 	(void) sigprocmask(SIG_SETMASK, &oset, NULL);
+-	(void) kill(0, signo);
++	(void) raise(signo);
+ 	errno = save_errno;
+ }
+EOF
+
 cflags="${EXTRA_TARGET_CFLAGS} -fPIC -I${TOOLS_PATH}/deps/include -I${TOOLS_PATH}/deps/include/ncursesw"
 ldflags="${EXTRA_TARGET_LDFLAGS} -L${TOOLS_PATH}/deps/lib"