13/11/2018 17:38, Burdick, Cliff: > > -----Original Message----- > From: Thomas Monjalon [mailto:tho...@monjalon.net] > Sent: Tuesday, November 13, 2018 8:07 AM > To: Burdick, Cliff > Cc: Burakov, Anatoly; dev@dpdk.org > Subject: Re: [dpdk-dev] [PATCH 1/1] eal: Don't fail secondary if primary is > missing tailqs > > 13/11/2018 16:45, Burdick, Cliff: > > From: Burakov, Anatoly [mailto:anatoly.bura...@intel.com] > > > On 13-Nov-18 9:21 AM, Thomas Monjalon wrote: > > > > 13/11/2018 00:33, Burdick, Cliff: > > > >> This patch was submitted by Jean Tourrilhes over two years ago, > > > >> but didn't receive any responses. I hit the same issue recently > > > >> when trying to use cgo (Golang) as a primary process linked to > > > >> libdpdk.a against a C++ application linked against the same > > > >> library.> > > > > > > > > > > The question is to know why you don't have the same constructors > > > > in primary and seconday? > > > > > > I've hit similar things in the past. I believe it was caused by our build > > > system stripping out unused libraries (such as rte_hash) from the binary > > > and thus not calling the constructor in the primary, but doing so in the > > > secondary (or something to that effect). > > > In any case, this is caused by linking different number of libraries to > > > primary and secondary, and should probably be fixed in the build system, > > > not in the tailqs code (unless we specifically support having different > > > linked libraries to primary and secondary?). > > > > Right, I think the original author of the patch stated the reasons in the > > link I provided. The build system seems like the most appropriate place to > > fix it, but the patch got me going quickly. I think the question is whether > > you want DPDK to support these other ways of linking. I'm certainly not the > > first to use cgo, since there's a virtual switch project doing the same: > > > > https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_lagopu > > s_vsw&d=DwICAg&c=jcv3orpCsv7C4ly8-ubDoUfrxF5xIGWmptxGWP5vi5w&r=m1RLQOG > > Okz9MauvVLZmiGtyWc5mA7DejbPFNE1IDj-4&m=hQqVCNwW7eoEzB_hLFK97i8idS8FIqX > > oPeclwsIZq7Y&s=BMoBlwkqljwWIBY3SE3pPMCfVnOUlDuZLrno4-SojKM&e= > > > > They don't use primary/secondary processes, though, so the issue is never > > hit. I'm in a situation where using cgo seemed like the easiest path to > > accomplish what I'm doing since I needed specialized libraries for it that > > were not available in C/C++. At some point I bet someone would use Cython > > to start linking against DPDK as well, and we'd likely run into the same > > issue. > > >For sure, we want to support using DPDK with cgo or cython. > >But it is not clear what is the relation with not having the same > >compilation for primary and secondary. Please could you elaborate? > > Hi Thomas, I think Jean explained it well here: > https://dev.dpdk.narkive.com/ZM3a7QD1/dpdk-dev-bug-static-constructors-considered-evil > > "The build system of the application does not have all the > subtelties of the DPDK build system, and ends up including *all* the > constructors, wether they are used or not in the code. Moreover, they > are included in a different order. Actually, by default the builds > include no constructors at all (which is a big fail), so the library > needs to be included with --whole-archive (see Snort DPDK > instructions)." > > I will get to the bottom of my exact case to understand what's happening, but > my primary application is a cgo application that I'm linking to by using > almost exactly the same flags that are used in the DPDK build system to build > examples. The DPDK libraries I'm linking against is a single location for > both primary and secondary; in other words, I don't build DPDK twice.
OK I understand, thanks. > You had alluded to a pkg-config for DPDK in the 2015 thread, which cgo can > use, but I don't know if that ever was implemented. Cgo can use pkg-config if > it's available, otherwise the only tools are specifying LDFLAGS and CFLAGS > into their build system. Yes, the right answer is still pkg-config :) The good news is that it is now implemented thanks to the meson build system: http://git.dpdk.org/dpdk/tree/doc/build-sdk-meson.txt#n182