win32: emulate SIGPIPE

The code to check whether a write error is due to a broken pipe
can now either:

- return with error EPIPE;
- cause the process to exit with code 128+SIGPIPE.

The default is the latter but the behaviour can be changed by issuing
signal(SIGPIPE, SIG_IGN) and signal(SIGPIPE, SIG_DFL) calls.

No actual signal is involved so kill can't send SIGPIPE and handlers
other than SIG_IGN and SIG_DFL aren't supported.

This does, however, avoid unsightly 'broken pipe' errors from commands
like the example in GitHub issue #99:

  dd if=/dev/urandom | tr -dc _A-Z-a-z-0-9 | head -c${1:-32};echo;

7 files changed, 32 insertions, 14 deletions

diff --git a/archival/tar.c b/archival/tar.c
index 22ad0e0f2..7dd89a282 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -1122,9 +1122,7 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
 
         if (opt & OPT_2COMMAND) {
                 putenv((char*)"TAR_FILETYPE=f");
-#ifdef SIGPIPE
                 signal(SIGPIPE, SIG_IGN);
-#endif
                 tar_handle->action_data = data_extract_to_command;
                 IF_FEATURE_TAR_TO_COMMAND(tar_handle->tar__to_command_shell = xstrdup(get_shell_name());)
         }
diff --git a/coreutils/tee.c b/coreutils/tee.c
index d0ded58c4..f0ec791bb 100644
--- a/coreutils/tee.c
+++ b/coreutils/tee.c
@@ -69,11 +69,9 @@ int tee_main(int argc, char **argv)
                 signal(SIGINT, SIG_IGN); /* TODO - switch to sigaction. (why?) */
         }
         retval = EXIT_SUCCESS;
-#ifdef SIGPIPE
         /* gnu tee ignores SIGPIPE in case one of the output files is a pipe
          * that doesn't consume all its input.  Good idea... */
         signal(SIGPIPE, SIG_IGN);
-#endif
 
         /* Allocate an array of FILE *'s, with one extra for a sentinel. */
         fp = files = xzalloc(sizeof(FILE *) * (argc + 2));
diff --git a/include/libbb.h b/include/libbb.h
index 4ac749fd3..a17da9c1f 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -536,9 +536,7 @@ enum {
 #endif
                 + (1LL << SIGINT)
                 + (1LL << SIGTERM)
-#ifdef SIGPIPE
                 + (1LL << SIGPIPE)   // Write to pipe with no readers
-#endif
 #ifdef SIGQUIT
                 + (1LL << SIGQUIT)   // Quit from keyboard
 #endif
diff --git a/include/mingw.h b/include/mingw.h
index a1869227d..8a695d2d2 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -93,10 +93,14 @@ IMPL(getpwent,struct passwd *,NULL,void)
  * signal.h
  */
 #define SIGKILL 9
+#define SIGPIPE 13
 
 #define SIG_UNBLOCK 1
 
 NOIMPL(FAST_FUNC sigprocmask_allsigs, int how UNUSED_PARAM);
+typedef void (*sighandler_t)(int);
+sighandler_t winansi_signal(int signum, sighandler_t handler);
+#define signal(s, h) winansi_signal(s, h)
 
 /*
  * stdio.h
diff --git a/libbb/u_signal_names.c b/libbb/u_signal_names.c
index f7d598c7a..036ad0038 100644
--- a/libbb/u_signal_names.c
+++ b/libbb/u_signal_names.c
@@ -27,6 +27,10 @@
 
 #include "libbb.h"
 
+#if ENABLE_PLATFORM_MINGW32
+# undef SIGPIPE
+#endif
+
 /* Believe it or not, but some arches have more than 32 SIGs!
  * HPPA: SIGSTKFLT == 36. */
 
diff --git a/shell/ash.c b/shell/ash.c
index 22dedc1b6..2e3b22850 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -4410,11 +4410,7 @@ sprint_status48(char *s, int status, int sigonly)
 #endif
                         st = WTERMSIG(status);
                 if (sigonly) {
-#ifdef SIGPIPE
                         if (st == SIGINT || st == SIGPIPE)
-#else
-                        if (st == SIGINT)
-#endif
                                 goto out;
 #if JOBS
                         if (WIFSTOPPED(status))
@@ -14951,7 +14947,7 @@ forkshell_openhere(struct forkshell *fs)
         ignoresig(SIGQUIT); //signal(SIGQUIT, SIG_IGN);
         ignoresig(SIGHUP);  //signal(SIGHUP, SIG_IGN);
         ignoresig(SIGTSTP); //signal(SIGTSTP, SIG_IGN);
-        //signal(SIGPIPE, SIG_DFL);
+        signal(SIGPIPE, SIG_DFL);
         if (redir->type == NHERE) {
                 size_t len = strlen(redir->nhere.doc->narg.text);
                 full_write(pip[1], redir->nhere.doc->narg.text, len);
diff --git a/win32/winansi.c b/win32/winansi.c
index a8f5dba79..167b4b0b1 100644
--- a/win32/winansi.c
+++ b/win32/winansi.c
@@ -475,12 +475,32 @@ int winansi_puts(const char *s)
         return (winansi_fputs(s, stdout) == EOF || putchar('\n') == EOF) ? EOF : 0;
 }
 
+static sighandler_t sigpipe_handler = SIG_DFL;
+
+#undef signal
+sighandler_t winansi_signal(int signum, sighandler_t handler)
+{
+        sighandler_t old;
+
+        if (signum == SIGPIPE) {
+                old = sigpipe_handler;
+                sigpipe_handler = handler;
+                return old;
+        }
+        return signal(signum, handler);
+}
+
 static void check_pipe_fd(int fd)
 {
-        if (GetLastError() == ERROR_NO_DATA) {
-                if (GetFileType((HANDLE)_get_osfhandle(fd)) == FILE_TYPE_PIPE) {
+        int error = GetLastError();
+
+        if ((error == ERROR_NO_DATA &&
+                        GetFileType((HANDLE)_get_osfhandle(fd)) == FILE_TYPE_PIPE) ||
+                        error == ERROR_BROKEN_PIPE) {
+                if (sigpipe_handler == SIG_DFL)
+                        exit(128+SIGPIPE);
+                else /* SIG_IGN */
                         errno = EPIPE;
-                }
         }
 }