Libguestfs - Apr 2020 - Re: [PATCH nbdkit v3 2/2] golang: Compile against the local nbdkit build, not installed.

Version 2:
https://www.redhat.com/archives/libguestfs/2020-April/thread.html#00166

Version 3 contains all changes discussed in the previous review.

Rich.

If you want to compile against a locally compiled (but not installed)
nbdkit, you can now set PKG_CONFIG_PATH=/path/to/nbdkit/server/local

Since it's not clear how useful this will be (we only want it for
internal reasons) this is not documented.

Thanks: Dan Berrangé, Eric Blake
---
 .gitignore                |  1 +
 configure.ac              |  1 +
 server/local/nbdkit.pc.in | 43 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+)

diff --git a/.gitignore b/.gitignore
index 4f6fcf1b..8c701295 100644
--- a/.gitignore
+++ b/.gitignore
@@ -83,6 +83,7 @@ plugins/*/*.3
 /plugins/tar/nbdkit-tar-plugin
 /plugins/tmpdisk/default-command.c
 /podwrapper.pl
+/server/local/nbdkit.pc
 /server/nbdkit
 /server/nbdkit.pc
 /server/synopsis.c
diff --git a/configure.ac b/configure.ac
index b71d9d8c..17d8d676 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1088,6 +1088,7 @@ AC_CONFIG_FILES([Makefile
                  filters/truncate/Makefile
                  filters/xz/Makefile
                  fuzzing/Makefile
+                 server/local/nbdkit.pc
                  server/Makefile
                  server/nbdkit.pc
                  tests/functions.sh
diff --git a/server/local/nbdkit.pc.in b/server/local/nbdkit.pc.in
new file mode 100644
index 00000000..1d8b6bee
--- /dev/null
+++ b/server/local/nbdkit.pc.in
@@ -0,0 +1,43 @@
+# nbdkit
+# Copyright (C) 2013-2020 Red Hat Inc.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+# * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# * Neither the name of Red Hat nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS
IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+# This alternate pkg-config file may be used to compile plugins
+# against a locally compiled (but not installed) nbdkit.
+
+prefix=@abs_top_builddir@
+exec_prefix=@abs_top_builddir@
+
+Name: @PACKAGE_NAME@
+Version: @PACKAGE_VERSION@
+Description: A toolkit for creating NBD servers
+Requires:
+Cflags: -I@abs_top_srcdir@/include -I@abs_top_builddir@/include
+Libs:
-- 
2.18.2

Compiling nbdkit from source when an older nbdkit is installed would
fail because certain symbols such as .get_ready are not defined in the
(installed) <nbdkit-plugin.h>:

  ../../src/libguestfs.org/nbdkit/nbdkit.go:541:8: plugin.get_ready undefined
(type _Ctype_struct_nbdkit_plugin has no field or method get_ready)

Of course we should be compiling against the local
include/nbdkit-plugin.h file.

We don't want to modify the *.go files themselves as they might be
copied into other projects.  Instead we can set PKG_CONFIG_PATH to
point to server/local/nbdkit.pc which will return the correct CFLAGS.

Fixes: commit 1ff44288ae1cf95428283e252edd9474c3fe3b55
Thanks: Dan Berrangé, Eric Blake
---
 plugins/golang/Makefile.am | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/plugins/golang/Makefile.am b/plugins/golang/Makefile.am
index f189184c..10ccea18 100644
--- a/plugins/golang/Makefile.am
+++ b/plugins/golang/Makefile.am
@@ -66,18 +66,21 @@ noinst_DATA = \
 examples/dump-plugin/nbdkit-godump-plugin.so: \
 	    $(plugin_sources) examples/dump-plugin/dumpplugin.go
 	cd examples/dump-plugin && \
+
PKG_CONFIG_PATH="$(abs_builddir)/server/local$${PKG_CONFIG_PATH:-:$$PKG_CONFIG_PATH}"
\
 	GOPATH="$(abs_builddir)" \
 	$(GOLANG) build -o nbdkit-godump-plugin.so -buildmode=c-shared
 
 examples/minimal/nbdkit-gominimal-plugin.so: \
 	    $(plugin_sources) examples/minimal/minimal.go
 	cd examples/minimal && \
+
PKG_CONFIG_PATH="$(abs_builddir)/server/local$${PKG_CONFIG_PATH:-:$$PKG_CONFIG_PATH}"
\
 	GOPATH="$(abs_builddir)" \
 	$(GOLANG) build -o nbdkit-gominimal-plugin.so -buildmode=c-shared
 
 examples/ramdisk/nbdkit-goramdisk-plugin.so: \
 	    $(plugin_sources) examples/ramdisk/ramdisk.go
 	cd examples/ramdisk && \
+
PKG_CONFIG_PATH="$(abs_builddir)/server/local$${PKG_CONFIG_PATH:-:$$PKG_CONFIG_PATH}"
\
 	GOPATH="$(abs_builddir)" \
 	$(GOLANG) build -o nbdkit-goramdisk-plugin.so -buildmode=c-shared
 
@@ -87,6 +90,7 @@ check_DATA = test/nbdkit-gotest-plugin.so
 
 test/nbdkit-gotest-plugin.so: $(plugin_sources) test/test.go
 	cd test && \
+
PKG_CONFIG_PATH="$(abs_builddir)/server/local$${PKG_CONFIG_PATH:-:$$PKG_CONFIG_PATH}"
\
 	GOPATH="$(abs_builddir)" \
 	$(GOLANG) build -o nbdkit-gotest-plugin.so -buildmode=c-shared
 
-- 
2.18.2

On 4/23/20 2:13 PM, Richard W.M. Jones wrote:
> Version 2:
> https://www.redhat.com/archives/libguestfs/2020-April/thread.html#00166
> 
> Version 3 contains all changes discussed in the previous review.
Looks good now.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

On 4/23/20 2:13 PM, Richard W.M. Jones wrote:
> Compiling nbdkit from source when an older nbdkit is installed would
> fail because certain symbols such as .get_ready are not defined in the
> (installed) <nbdkit-plugin.h>:
> 
>    ../../src/libguestfs.org/nbdkit/nbdkit.go:541:8: plugin.get_ready
undefined (type _Ctype_struct_nbdkit_plugin has no field or method get_ready)
> 
> Of course we should be compiling against the local
> include/nbdkit-plugin.h file.
> 
> We don't want to modify the *.go files themselves as they might be
> copied into other projects.  Instead we can set PKG_CONFIG_PATH to
> point to server/local/nbdkit.pc which will return the correct CFLAGS.
> 
> Fixes: commit 1ff44288ae1cf95428283e252edd9474c3fe3b55
> Thanks: Dan Berrangé, Eric Blake
> ---
> +++ b/plugins/golang/Makefile.am
> @@ -66,18 +66,21 @@ noinst_DATA = \
>   examples/dump-plugin/nbdkit-godump-plugin.so: \
>   	    $(plugin_sources) examples/dump-plugin/dumpplugin.go
>   	cd examples/dump-plugin && \
> +
PKG_CONFIG_PATH="$(abs_builddir)/server/local$${PKG_CONFIG_PATH:-:$$PKG_CONFIG_PATH}"
\
Ooops, I typod this one.

unset foo
barblah=set
echo "pre${foo:-:$foo}"
echo "pre${bar:-:$bar}"
echo "pre${bar:-:$blah}"

shows that :- was the wrong operator.  Better is :+.

All four sites need it.

But even then, I'm still getting build failures; and make V=1 shows that 
PKG_CONFIG_PATH is getting set correctly :(



-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org