Hi Thomas, Thanks for the review.
The use case that made me see this is that I configured the dpdk using meson option "-- default_library=static" in conjunction with buildroot which is patching meson to prefer static libraries in this case. This causes the link line generated from the dependency() directive to result in an expanded "/path/to/libpcap.a". The dpdk_extra_ldflags += '-lpcap' is a direct (manual) addition to the link line that cannot be changed in the same way. In this specific setup, the change is the following: Before: -lpcap /path/to/libpcap.a After: /path/to/libpcap.a I admit this is quite the corner case (and probably not a great idea). I will replace that confusing second paragraph with the comment you made regarding " ext_deps += pcap_dep". Best regards, On Fri, Apr 9, 2021 at 12:39 AM Thomas Monjalon <tho...@monjalon.net> wrote: > Thank you, the fix looks good. > I would like to improve the explanation. > > If I understand the issue, the title should be > "build: remove redundant libpcap link" > > 26/03/2021 09:22, Gabriel Ganne: > > libpcap is already found and registered as a dependency by meson, and > > the dependency is already correctly used in librte_port. This line is > > just unnecessary. > > To be precise, the pcap PMD and the librte_port both declare their > dependency to libpcap with a line "ext_deps += pcap_dep" > and meson automatically adds this dependency to the pkg-config file > in the private section for static builds. > That's why it is not needed to add the dependency explicitly > in dpdk_extra_ldflags (involved in static build with pkg-config). > > > It also has the side effect of messing with the meson link line: dpdk > > Which "link line"? > > > link will be declared twice: manually and then through pkg-config. If > > What is "manually"? > > > you configure meson to prefer static linking over dynamic, this will > > No need to configure meson for that. Static linking can be tested with > make in an example. Please avoid messing with meson explanation > for application linking, it is already complicate enough :) > > > cause the build to fail on librte_port, since the pcap deps are not yet > > seen by the linker. > > Sorry it is not clear to me. > I think it would help to see a before/after effect on the link command. > Something like: > > before: > Libs.private: -lpcap > Requires.private: libpcap > after: > Libs.private: > Requires.private: libpcap > > [...] > > - dpdk_extra_ldflags += '-lpcap' > > > > -- Gabriel Ganne
