From a0fe78cfdc086879e41f5980bb1679b4514f3e61 Mon Sep 17 00:00:00 2001
From: f18m <francesco.montorsi@gmail.com>
Date: Tue, 31 Oct 2023 15:58:21 +0100
Subject: [PATCH] Fix compat issue with Asciidoctor 1.5.8 used by Debian10

---
 doc/Makefile.am | 12 +++++++++---
 doc/zmq.adoc    |  4 ++--
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/doc/Makefile.am b/doc/Makefile.am
index de710d3ab5..b6c1c4df20 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -51,12 +51,18 @@ EXTRA_DIST += $(MAN_HTML) $(MAN_DOC)
 MAINTAINERCLEANFILES += $(MAN_HTML) $(MAN_DOC)
 SUFFIXES=.html .adoc .3 .7
 
+
+# NOTE: libzmq CI runs on some "old" distribution that ships Asciidoctor 1.5.x which has 
+#       some small incompatibility with Asciidoctor 2.x; in particular 2.x exposes automatically
+#       the "backend" attribute that can be used inside .adoc documents; 1.5.x did not, so we
+#       provide the "zmq_output_format" attribute as compat alternative to "backend" built-in attribute
+
 .adoc.html: 
-	asciidoctor -b html -azmq_version=@PACKAGE_VERSION@  $<
+	asciidoctor --backend html --attribute zmq_output_format=html --attribute zmq_version=@PACKAGE_VERSION@  $<
 .adoc.3:
-	asciidoctor -b manpage -azmq_version=@PACKAGE_VERSION@  $<
+	asciidoctor --backend manpage --attribute zmq_output_format=manpage --attribute zmq_version=@PACKAGE_VERSION@  $<
 .adoc.7:
-	asciidoctor -b manpage -azmq_version=@PACKAGE_VERSION@  $<
+	asciidoctor --backend manpage --attribute zmq_output_format=manpage --attribute zmq_version=@PACKAGE_VERSION@  $<
 
 dist-hook : $(MAN_DOC) $(MAN_HTML)
 
diff --git a/doc/zmq.adoc b/doc/zmq.adoc
index c82bcdd91b..9eee03162b 100644
--- a/doc/zmq.adoc
+++ b/doc/zmq.adoc
@@ -1,4 +1,4 @@
-ifeval::["{backend}" == "manpage"]
+ifeval::["{zmq_output_format}" == "manpage"] 
 
 = zmq(7)
 
@@ -11,7 +11,7 @@ zmq - 0MQ lightweight messaging kernel, version {zmq_version}
 *cc* ['flags'] 'files' *-lzmq* ['libraries']
 
 endif::[]
-ifeval::["{backend}" != "manpage"]
+ifeval::["{zmq_output_format}" != "manpage"]
 = ZMQ API Reference
 endif::[]