[PATCH] xap_helper: test cleanup + throw support in C++

[Eric Wong <e@80x24.org>]

Eric Wong <e@80x24.org> wrote:
> In case somebody reviewing this code gets curious.

And just in case we encounter other C++ implementations:
-------8<-------
Subject: [PATCH] xap_helper: test cleanup + throw support in C++

We need to ensure whatever C++ compiler gets used supports this
GNU extension as we expect it to.  clang 13 and 14 and g++ 10
all work as we expect it to.
---
 side note: sadly, longjmp/siglongjmp(3) in POSIX does not trigger
 __cleanup__

 lib/PublicInbox/xap_helper.h | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/lib/PublicInbox/xap_helper.h b/lib/PublicInbox/xap_helper.h
index 2322d062..377ff45a 100644
--- a/lib/PublicInbox/xap_helper.h
+++ b/lib/PublicInbox/xap_helper.h
@@ -578,12 +578,27 @@ static bool cmd_dump_roots(struct req *req)
 	return true;
 }
 
-// internal usage only
+// for test usage only, we need to ensure the compiler supports
+// __cleanup__ when exceptions are thrown
+struct inspect { struct req *req; };
+
+static void inspect_ensure(struct inspect *x)
+{
+	fprintf(x->req->fp[0], "pid=%d has_threadid=%d",
+		(int)getpid(), has_threadid(x->req->srch) ? 1 : 0);
+}
+
 static bool cmd_test_inspect(struct req *req)
 {
-	fprintf(req->fp[0], "pid=%d has_threadid=%d",
-		(int)getpid(), has_threadid(req->srch) ? 1 : 0);
-	return true;
+	__attribute__((__cleanup__(inspect_ensure))) struct inspect x;
+	x.req = req;
+	try {
+		throw Xapian::InvalidArgumentError("test");
+	} catch (Xapian::InvalidArgumentError) {
+		return true;
+	}
+	fputs("this should not be printed", req->fp[0]);
+	return false;
 }
 
 #define CMD(n) { .fn_len = sizeof(#n) - 1, .fn_name = #n, .fn = cmd_##n }