[PATCH 04/12] Windows: Fix run/attach hang after bad run/attach

[Pedro Alves <pedro@palves.net>]

On Cygwin, gdb.base/attach.exp exposes that an "attach" after a
previously failed "attach" hangs:

 (gdb) PASS: gdb.base/attach.exp: do_attach_failure_tests: attach to digits-starting nonsense is prohibited
 attach 0
 Can't attach to process 0 (error 2: The system cannot find the file specified.)
 (gdb) PASS: gdb.base/attach.exp: do_attach_failure_tests: attach to nonexistent process is prohibited
 attach 10644
 FAIL: gdb.base/attach.exp: do_attach_failure_tests: first attach (timeout)

The problem is that windows_nat_target::attach always returns success
even if the attach fails.  When we return success, the helper thread
begins waiting for events (which will never come), and thus the next
attach deadlocks on the do_synchronously call within
windows_nat_target::attach.

"run" has the same problem, which is exposed by the new
gdb.base/run-fail-twice.exp testcase added in a following patch:

 (gdb) run
 Starting program: .../gdb.base/run-fail-twice/run-fail-twice.nox
 Error creating process .../gdb.base/run-fail-twice/run-fail-twice.nox, (error 6: The handle is invalid.)
 (gdb) PASS: gdb.base/run-fail-twice.exp: test: bad run 1
 run
 Starting program: .../gdb.base/run-fail-twice/run-fail-twice.nox
 FAIL: gdb.base/run-fail-twice.exp: test: bad run 2 (timeout)

The problem here is the same, except that this time it is
windows_nat_target::create_inferior that returns the incorrect result.

This commit fixes both the "attach" and "run" paths, and the latter
both the Cygwin and MinGW paths.  The tests mentioned above now pass
on Cygwin.  Confirmed the fixes manually for MinGW GDB.

Change-Id: I15ec9fa279aff269d4982b00f4ea7c25ae917239
---
 gdb/windows-nat.c | 35 ++++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index a53b6a6e053..d61ed95a7fb 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -2059,7 +2059,7 @@ windows_nat_target::attach (const char *args, int from_tty)
       if (!ok)
 	err = (unsigned) GetLastError ();
 
-      return true;
+      return ok;
     });
 
   if (err.has_value ())
@@ -2784,12 +2784,15 @@ windows_nat_target::create_inferior (const char *exec_file,
   windows_init_thread_list ();
   do_synchronously ([&] ()
     {
-      if (!create_process (nullptr, args, flags, w32_env,
-			   inferior_cwd != nullptr ? infcwd : nullptr,
-			   disable_randomization,
-			   &si, &pi))
+      BOOL ok = create_process (nullptr, args, flags, w32_env,
+				inferior_cwd != nullptr ? infcwd : nullptr,
+				disable_randomization,
+				&si, &pi);
+
+      if (!ok)
 	ret = (unsigned) GetLastError ();
-      return true;
+
+      return ok;
     });
 
   if (w32_env)
@@ -2910,16 +2913,18 @@ windows_nat_target::create_inferior (const char *exec_file,
   windows_init_thread_list ();
   do_synchronously ([&] ()
     {
-      if (!create_process (nullptr, /* image */
-			   args,	/* command line */
-			   flags,	/* start flags */
-			   w32env,	/* environment */
-			   inferior_cwd, /* current directory */
-			   disable_randomization,
-			   &si,
-			   &pi))
+      BOOL ok = create_process (nullptr, /* image */
+				args,	/* command line */
+				flags,	/* start flags */
+				w32env,	/* environment */
+				inferior_cwd, /* current directory */
+				disable_randomization,
+				&si,
+				&pi);
+      if (!ok)
 	ret = (unsigned) GetLastError ();
-      return true;
+
+      return ok;
     });
   if (tty != INVALID_HANDLE_VALUE)
     CloseHandle (tty);
-- 
2.43.2