10/11/2020 14:19, Bruce Richardson: > On Tue, Nov 10, 2020 at 02:04:21PM +0100, Thomas Monjalon wrote: > > 10/11/2020 12:34, Bruce Richardson: > > > On Tue, Nov 10, 2020 at 12:25:13PM +0100, Thomas Monjalon wrote: > > > > 10/11/2020 11:08, Bruce Richardson: > > > > > On Mon, Nov 09, 2020 at 08:26:10PM +0100, Thomas Monjalon wrote: > > > > > > 09/11/2020 19:02, Bruce Richardson: > > > > > > > On Mon, Nov 09, 2020 at 06:09:51PM +0100, Thomas Monjalon wrote: > > > > > > > > 27/10/2020 18:38, Bruce Richardson: > > > > > > > > > To test the installation process of DPDK using "ninja install" > > > > > > > > > test-meson-builds.sh builds a subset of the examples using > > > > > > > > > "make". > > > > > > > > > To allow more flexibility for people testing, allow the set of > > > > > > > > > examples chosen for this make test to be overridden using > > > > > > > > > variable > > > > > > > > > "DPDK_BUILD_TEST_EXAMPLES" in the environment. > > > > > > > > > > > > > > > > > > Since a number of example apps link against drivers directly > > > > > > > > > even > > > > > > > > > for shared builds, we need to ensure that LD_LIBRARY_PATH > > > > > > > > > points to > > > > > > > > > the main DPDK lib folder so any dependencies of those drivers > > > > > > > > > can > > > > > > > > > be found e.g. that the PCI/vdev bus driver .so is found. [All > > > > > > > > > drivers are symlinked from drivers dir back to lib dir on > > > > > > > > > install, > > > > > > > > > so only one dir rather than two is needed in the path.] > > > > > > > > [...] > > > > > > > > > +libdir=$(dirname $(find $DESTDIR -name librte_eal.so)) > > > > > > > > > +export > > > > > > > > > LD_LIBRARY_PATH=$libdir:$LD_LIBRARY_PATH > > > > > > > > > > > > > > > > I don't get why libdir is required for some examples, and not > > > > > > > > for > > > > > > > > others? The pkg-config file is not enough? > > > > > > > > > > > > > > > > > > > > > > It's only needed for examples that link against drivers directly. > > > > > > > > > > > > > > I believe it's needed in those cases, because app linker flags > > > > > > > (including e.g. -lrte_pmd_bond) occur before the pkg-config flags, > > > > > > > which means that the linker at that point does not have the path > > > > > > > to > > > > > > > find the dependencies of the driver. [In a normal build, this > > > > > > > wouldn't > > > > > > > be necessary because the library directory would be a standard > > > > > > > path] > > > > > > > > > > > > If it's just a matter of ordering, it would be a better example to > > > > > > fix > > > > > > the ordering in the Makefile, isn't it? > > > > > > > > > > > > > > > > I thought about that, but it seems strange to have the DPDK linker > > > > > flags > > > > > appear before the application specific flags. The general style is to > > > > > have > > > > > the apps own linker flags apply first, and then the list of > > > > > dependencies, > > > > > so that any app linker flags take precedence. The other option is to > > > > > have > > > > > two separate LDFLAG variables for the app, one for before pkg-config > > > > > flags > > > > > and the other afterwards, but that is an untidy solution. > > > > > > > > > > Therefore, I think it's better to keep the ordering in the examples > > > > > as-is > > > > > and just set the library path in the script. It's only a single extra > > > > > assignment that is necessary because we are installing to a > > > > > non-standard > > > > > path using DESTDIR. > > > > > > > > It is OK to add LD_LIBRARY_PATH in test-meson-builds.sh because > > > > DPDK is "installed" with a DESTDIR prefix. > > > > > > > > But this change is unrelated to test more examples, > > > > it is a general fix for examples compilation. > > > > The thing I'm missing, as I said above, > > > > "why libdir is required for some examples, and not for others?" > > > > I feel something wrong made linking work where it should not. > > > > > > > > > > As I explained above, libdir is required for examples that link directly > > > against DPDK drivers in shared builds. There are only a few examples that > > > do so, which is why the majority worked fine, and why this was not needed > > > before. > > > > Sorry I don't understand how we link other libraries without > > LD_LIBRARY_PATH. > > Where the library path was taken from before this change? > > > > pkg-config outputs the library path via -L flag for all the other > libraries, which is why they are picked up. Right now the flags passed are > (in the case of the bonding example app): > > LDFLAGS += -lrte_net_bond > ... > LDFLAGS_SHARED = $(shell $(PKGCONF) --libs libdpdk) > ... > build/$(APP)-shared: $(SRCS-y) Makefile $(PC_FILE) | build > $(CC) $(CFLAGS) $(SRCS-y) -o $@ $(LDFLAGS) $(LDFLAGS_SHARED) > > which resolves to (roughly): > "-lrte_net_bond -L/path/to/dpdk/libs -lrte_ethdev ..."
This is the part I still don't understand. How it can resolve to path including DESTDIR? In my test, it resolves to -L/usr/local/lib so it cannot work. > This means that all the regular DPDK libs are found based off the "-L" > flag, but the rte_net_bond and its dependencies are not as they occur > before the -L flag. > > The alternative, as you suggested previously, is to move the -lrte_net_bond > to the end of the list, but that strikes me as less elegant as the LDFLAGS > for the app need to be split into two. > > A third choice is to modify the makefiles to use pkg-config "--libs-only-L" > flag to put in the relevant pkg-config path flag before the rte_net_bond. > (However, I have yet to check that all versions of pkg-config support this > flag, since we've been bitten in the past of using flags supported by only > some versions on some distros!) > > LDFLAGS += $(shell $(PKGCONF) --libs-only-L libdpdk) -lrte_net_bond > > Overall, given we are looking at a test script where we install to a > non-standard location, putting that location in the LD_LIBRARY_PATH seems > the easiest, sane solution. It also most closely matches real-world use, > where if one installs DPDK to a novel location, the path to the library > folder does need to be set somewhere for the runtime loader to find the > libs. I agree with setting LD_LIBRARY_PATH in the test script because of the "non-standard location". This is not a question.
