[dpdk-dev] [PATCH] mk: enable next abi in static libs

[Thomas Monjalon <thomas.monjalon@6wind.com>]

When a change makes really hard to keep ABI compatibility,
instead of waiting next release to break the ABI, it is smoother
to introduce the new code and enable it only for static libraries.
The flag RTE_NEXT_ABI may be used to "ifdef" the new code.
When the release is out, a dynamically linked application can use
the new shared libraries without rebuild while developpers can prepare
their application for the next ABI by reading the deprecation notice
and easily testing the new code.
When starting the next release cycle, the "ifdefs" will be removed
and the ABI break will be marked by incrementing LIBABIVER.

The new option CONFIG_RTE_NEXT_ABI is not defined in the configuration
templates because it is deduced from CONFIG_RTE_BUILD_SHARED_LIB.
It is automatically enabled for static libraries and disabled for
shared libraries.
It can be forced to another value by editing the generated .config file.
It shouldn't be enabled for shared libraries because it would break the
ABI without changing the version number LIBABIVER. That's why a warning
is printed in this case.

The guideline is also updated to integrate this new possibility.

Signed-off-by: Thomas Monjalon <thomas.monjalon@6wind.com>
---
 doc/guides/guidelines/versioning.rst | 2 ++
 lib/Makefile                         | 4 ++++
 mk/rte.sdkconfig.mk                  | 3 +++
 pkg/dpdk.spec                        | 1 +
 scripts/validate-abi.sh              | 2 ++
 5 files changed, 12 insertions(+)

diff --git a/doc/guides/guidelines/versioning.rst b/doc/guides/guidelines/versioning.rst
index a1c9368..6bc2a8e 100644
--- a/doc/guides/guidelines/versioning.rst
+++ b/doc/guides/guidelines/versioning.rst
@@ -57,6 +57,8 @@ being provided. The requirements for doing so are:
 
 #. A full deprecation cycle, as explained above, must be made to offer
    downstream consumers sufficient warning of the change.
+   The changes may be shown and used in static builds before the deprecation
+   cycle by conditioning them with RTE_NEXT_ABI option.
 
 #. The ``LIBABIVER`` variable in the makefile(s) where the ABI changes are
    incorporated must be incremented in parallel with the ABI changes
diff --git a/lib/Makefile b/lib/Makefile
index 5f480f9..ebf56ba 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -31,6 +31,10 @@
 
 include $(RTE_SDK)/mk/rte.vars.mk
 
+ifeq '$(CONFIG_RTE_BUILD_SHARED_LIB)$(CONFIG_RTE_NEXT_ABI)' 'yy'
+$(info WARNING: Shared libraries versioning is tainted!)
+endif
+
 DIRS-y += librte_compat
 DIRS-$(CONFIG_RTE_LIBRTE_EAL) += librte_eal
 DIRS-$(CONFIG_RTE_LIBRTE_MALLOC) += librte_malloc
diff --git a/mk/rte.sdkconfig.mk b/mk/rte.sdkconfig.mk
index f8d95b1..135825c 100644
--- a/mk/rte.sdkconfig.mk
+++ b/mk/rte.sdkconfig.mk
@@ -77,6 +77,9 @@ $(RTE_OUTPUT)/.config: $(RTE_CONFIG_TEMPLATE) FORCE | $(RTE_OUTPUT)
 		$(CPP) -undef -P -x assembler-with-cpp \
 		-ffreestanding \
 		-o $(RTE_OUTPUT)/.config_tmp $(RTE_CONFIG_TEMPLATE) ; \
+		printf 'CONFIG_RTE_NEXT_ABI=' >> $(RTE_OUTPUT)/.config_tmp ; \
+		sed -n 's,CONFIG_RTE_BUILD_SHARED_LIB=,,p' $(RTE_OUTPUT)/.config_tmp | \
+		tr 'yn' 'ny' >> $(RTE_OUTPUT)/.config_tmp ; \
 		if ! cmp -s $(RTE_OUTPUT)/.config_tmp $(RTE_OUTPUT)/.config; then \
 			cp $(RTE_OUTPUT)/.config_tmp $(RTE_OUTPUT)/.config ; \
 			cp $(RTE_OUTPUT)/.config_tmp $(RTE_OUTPUT)/.config.orig ; \
diff --git a/pkg/dpdk.spec b/pkg/dpdk.spec
index 5f6ec6a..fb71ccc 100644
--- a/pkg/dpdk.spec
+++ b/pkg/dpdk.spec
@@ -82,6 +82,7 @@ make O=%{target} T=%{target} config
 sed -ri 's,(RTE_MACHINE=).*,\1%{machine},' %{target}/.config
 sed -ri 's,(RTE_APP_TEST=).*,\1n,'         %{target}/.config
 sed -ri 's,(RTE_BUILD_SHARED_LIB=).*,\1y,' %{target}/.config
+sed -ri 's,(RTE_NEXT_ABI=).*,\1n,'         %{target}/.config
 sed -ri 's,(LIBRTE_VHOST=).*,\1y,'         %{target}/.config
 sed -ri 's,(LIBRTE_PMD_PCAP=).*,\1y,'      %{target}/.config
 sed -ri 's,(LIBRTE_PMD_XENVIRT=).*,\1y,'   %{target}/.config
diff --git a/scripts/validate-abi.sh b/scripts/validate-abi.sh
index 1747b8b..4476433 100755
--- a/scripts/validate-abi.sh
+++ b/scripts/validate-abi.sh
@@ -157,6 +157,7 @@ git checkout $TAG1
 # Make sure we configure SHARED libraries
 # Also turn off IGB and KNI as those require kernel headers to build
 sed -i -e"$ a\CONFIG_RTE_BUILD_SHARED_LIB=y" config/defconfig_$TARGET
+sed -i -e"$ a\CONFIG_RTE_NEXT_ABI=n" config/defconfig_$TARGET
 sed -i -e"$ a\CONFIG_RTE_EAL_IGB_UIO=n" config/defconfig_$TARGET
 sed -i -e"$ a\CONFIG_RTE_LIBRTE_KNI=n" config/defconfig_$TARGET
 
@@ -198,6 +199,7 @@ git checkout $TAG2
 # Make sure we configure SHARED libraries
 # Also turn off IGB and KNI as those require kernel headers to build
 sed -i -e"$ a\CONFIG_RTE_BUILD_SHARED_LIB=y" config/defconfig_$TARGET
+sed -i -e"$ a\CONFIG_RTE_NEXT_ABI=n" config/defconfig_$TARGET
 sed -i -e"$ a\CONFIG_RTE_EAL_IGB_UIO=n" config/defconfig_$TARGET
 sed -i -e"$ a\CONFIG_RTE_LIBRTE_KNI=n" config/defconfig_$TARGET
 
-- 
2.4.2