ash: add support for INT trap

The trap builtin now handles INT.  As before, other signals (from
a limited list) are accepted but their traps don't have any effect.

There's some variability in how shells handle traps.  This patch
upholds that proud tradition.

Various changes are needed to make this work:

- Line editing has a new flag to ignore Ctrl-C.

- If INT is being trapped or ignored don't call raise_interrupt().

- A minimal implementation of dotrap() is provided.

- Call dotrap() when the read builtin or line input detect Ctrl-C.

- Adjust Ctrl-C detection when the INT trap is changed.

- Set may_have_traps when an INT trap is set.

Costs 368-448 bytes.

(GitHub issue #303)

1 files changed, 4 insertions, 0 deletions

diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index 9220ddeb3..45d4c33f5 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -3030,6 +3030,10 @@ int FAST_FUNC read_line_input(line_input_t *st, const char *prompt, char *comman
                          && ic_raw == initial_settings.c_cc[VINTR]
                         ) {
                                 /* Ctrl-C (usually) - stop gathering input */
+#if ENABLE_PLATFORM_MINGW32
+                                if (state->flags & IGNORE_CTRL_C)
+                                        break;
+#endif
                                 command_len = 0;
                                 break_out = -1; /* "do not append '\n'" */
                                 break;