don't use sigaltstack() with USE_ASAN #2529

README.md

@@ -428,13 +428,6 @@ If things break or seem otherwise lackluster, **please** consult the
   handy if you've got a reference to a valid <code>nccell</code> anyway.
 </details>
 
-<details>
-  <summary>I compiled with AddressSanitizer, and ASAN throws an exception on
-    program exit.</summary>
-  Yeah, I think it has something to do with our signal handling, don't know
-  yet, sorry.
-</details>
-
 <details>
  <summary>I ran my Notcurses program under <code>valgrind</code>/ASAN, and
     it shows memory leaks from <code>libtinfo.so</code>, what's up with that?</summary>

src/lib/unixsig.c

@@ -205,6 +205,10 @@ int setup_signals(void* vnc, bool no_quit_sigs, bool no_winch_sigs,
     handling_winch = true;
   }
   if(!no_quit_sigs){
+// AddressSanitizer doesn't want us to use sigaltstack(). we could force everyone
+// to export ASAN_OPTIONS=use_sigaltstack=0, or just not fuck with the alternate
+// signal stack when built with ASAN.
+#ifndef USE_ASAN
     alt_signal_stack.ss_sp = malloc(alt_signal_stack.ss_size);
     if(alt_signal_stack.ss_sp == NULL){
       fprintf(stderr, "warning: couldn't create alternate signal stack (%s)" NL, strerror(errno));
@@ -217,6 +221,7 @@ int setup_signals(void* vnc, bool no_quit_sigs, bool no_winch_sigs,
         alt_signal_stack.ss_sp = NULL;
       }
     }
+#endif
     memset(&sa, 0, sizeof(sa));
     fatal_callback = handler;
     sa.sa_sigaction = fatal_handler;

tools/builddef.h.in

@@ -1,5 +1,10 @@
 // Populated by CMake; not installed
+
+// if we're a DFSG build, we leave out references to certain demos
 #cmakedefine DFSG_BUILD
+
+// if we're an ASAN build, we don't use sigaltstack() ourselves
+#cmakedefine USE_ASAN
 #cmakedefine USE_DEFLATE
 #cmakedefine USE_GPM
 #cmakedefine USE_QRCODEGEN