bc: switch to SA_RESTART signal handling

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 17 insertions, 1 deletions

diff --git a/miscutils/bc.c b/miscutils/bc.c
index 15089314f..148e340a5 100644
--- a/miscutils/bc.c
+++ b/miscutils/bc.c
@@ -7121,7 +7121,23 @@ static BcStatus bc_vm_run(int argc, char *argv[],
 
         if (G.ttyin) {
 #if ENABLE_FEATURE_BC_SIGNALS
-                signal_no_SA_RESTART_empty_mask(SIGINT, record_signo);
+                // With SA_RESTART, most system calls will restart
+                // (IOW: they won't fail with EINTR).
+                // In particular, this means ^C won't cause
+                // stdout to get into "error state" if SIGINT hits
+                // within write() syscall.
+                // The downside is that ^C while line input is taken
+                // will only be handled after [Enter] since read()
+                // from stdin is not interrupted by ^C either,
+                // it restarts, thus fgetc() does not return on ^C.
+                signal_SA_RESTART_empty_mask(SIGINT, record_signo);
+
+                // Without SA_RESTART, this exhibits a bug:
+                // "while (1) print 1" and try ^C-ing it.
+                // Intermittently, instead of returning to input line,
+                // you'll get "output error: Interrupted system call"
+                // and exit.
+                //signal_no_SA_RESTART_empty_mask(SIGINT, record_signo);
 #endif
                 if (!(option_mask32 & BC_FLAG_Q))
                         bc_vm_info();