win32: ignore ctrl-c in parent of execve(2)

The execve(2) system call is emulated for Microsoft Windows.  This
requires the creation of a new process.  The old process remains
active, waiting for the "execed" child to exit so it can pass on
its exit status.

Previously this was achieved using P_WAIT mode in the call to
spawnve().  However the parent of the execve(2) process may still
be able to catch Ctrl-C interrupts.  This can lead to unwanted
behaviour, such as a shell and its children competing for input.

Force the waiting process to ignore Ctrl-C interrupts.

Costs 64-80 bytes.

(GitHub issue #303)

1 files changed, 14 insertions, 4 deletions

diff --git a/win32/process.c b/win32/process.c
index 428d6c703..1ee576055 100644
--- a/win32/process.c
+++ b/win32/process.c
@@ -408,21 +408,31 @@ mingw_spawn_proc(const char **argv)
         return mingw_spawnvp(P_NOWAIT, argv[0], (char *const *)argv);
 }
 
+static NORETURN void wait_for_child(HANDLE child)
+{
+        DWORD code;
+
+        SetConsoleCtrlHandler(NULL, TRUE);
+        WaitForSingleObject(child, INFINITE);
+        GetExitCodeProcess(child, &code);
+        exit((int)code);
+}
+
 int
 mingw_execvp(const char *cmd, char *const *argv)
 {
-        int ret = (int)mingw_spawnvp(P_WAIT, cmd, argv);
+        intptr_t ret = mingw_spawnvp(P_NOWAIT, cmd, argv);
         if (ret != -1 || errno == 0)
-                exit(ret);
+                wait_for_child((HANDLE)ret);
         return ret;
 }
 
 int
 mingw_execve(const char *cmd, char *const *argv, char *const *envp)
 {
-        int ret = (int)mingw_spawn_interpreter(P_WAIT, cmd, argv, envp, 0);
+        intptr_t ret = mingw_spawn_interpreter(P_NOWAIT, cmd, argv, envp, 0);
         if (ret != -1 || errno == 0)
-                exit(ret);
+                wait_for_child((HANDLE)ret);
         return ret;
 }