bpf2go: Allow multiple commands inside BPF2GO_CC

[jrife]

Allow multiple commands to be specified inside BPF2GO_CC. Example:

BPF2GO_CC="ccache clang" go generate ../pkg/a/b

I'm working on cilium/cilium#38693 where one of the checks uses ccache clang instead of just clang as the compile command substitution. Currently, this doesn't work with bpf2go. This change makes it possible to use the same compile command as the rest of the build in cases like this.

[lmb]

Out of curiosity, does the following work?

bpf2go -cc ccache ... -- clang

Hunch: this will fail because of overrideFlags being passed to ccache before clang. Not sure that ccache likes that. If that's the case we can be a bit smarter in Compile and insert overrideFlags at the position where the first flags starts with -.

[jrife]

Hunch: this will fail because of overrideFlags being passed to ccache before clang. Not sure that ccache likes that. If that's the case we can be a bit smarter in Compile and insert overrideFlags at the position where the first flags starts with -

Yeah, it won't work currently. And yes, you could reposition overrideFlags to make this possible:

bpf2go -cc ccache ... -- clang

However, from the perspective of using bpf2go in the same Makefile as a bunch of other build commands, it would be inconvenient to need to do some special handling around its invocation to, e.g., split apart my CC variable. I think it makes a lot of sense to allow this sort of thing to be passed through via BPF2GO_CC.

[jrife]

/test

[jrife]

@lmb Could you take another look at this when you get a chance? This is a blocker for me on cilium/cilium#38693

[lmb]

@jrife DCO is failing, please take a look at https://github.com/cilium/ebpf/pull/1829/checks?check_run_id=46950786710

[jrife]

@lmb

DCO is failing, please take a look at

Fixed. Author didn't match the Signed-off-by tag.

Also, switched back to Fields for the reasons I listed above and added a check to error out if ccParts is empty. Example:

BPF2GO_CC="   " BPF2GO_CFLAGS="-DSKIP_DEBUG=1 -DENABLE_IPV4=1 -DENABLE_IPV6=1 -DENABLE_ROUTING=1 -DPOLICY_VERDICT_NOTIFY=1 -DALLOW_ICMP_FRAG_NEEDED=1 -DENABLE_IDENTITY_MARK=1 -DMONITOR_AGGREGATION=3 -DCT_REPORT_FLAGS=0x0002 -DENABLE_HOST_FIREWALL=1 -DENABLE_ICMP_RULE=1 -DENABLE_CUSTOM_CALLS=1 -DENABLE_SRV6=1 -DENABLE_L7_LB=1 -DENABLE_MASQUERADE_IPV4=1 -DENABLE_IP_MASQ_AGENT_IPV4=1 -DENABLE_MASQUERADE_IPV6=1 -DENABLE_IP_MASQ_AGENT_IPV6=1 -DENABLE_SRC_RANGE_CHECK=1 -DENABLE_NODEPORT=1 -DENABLE_NODEPORT_ACCELERATION=1 -DENABLE_SESSION_AFFINITY=1 -DENABLE_DSR_ICMP_ERRORS=1 -DENABLE_DSR=1 -DENABLE_DSR_HYBRID=1 -DENABLE_IPV4_FRAGMENTS=1 -DENABLE_BANDWIDTH_MANAGER=1 -DENABLE_EGRESS_GATEWAY=1 -DENABLE_VTEP=1 -DENABLE_TPROXY=1 -DENABLE_HOST_ROUTING=1 -DENCAP_IFINDEX=1 -DTUNNEL_MODE=1 -DENABLE_MULTICAST=1 -DLB_SELECTION_PER_SERVICE=1 -DLB_SELECTION_MAGLEV=2 -DLB_SELECTION_RANDOM=1 -DENABLE_IPSEC=1 -I/go/src/github.com/cilium/cilium/bpf -I/go/src/github.com/cilium/cilium/bpf/include -O2 -g --target=bpf -std=gnu99 -nostdinc -ftrap-function=__undefined_trap -Wall -Wextra -Werror -Wshadow -Wno-address-of-packed-member -Wno-unknown-warning-option -Wno-gnu-variable-sized-type-not-at-end -Wimplicit-int-conversion -Wenum-conversion -Wimplicit-fallthrough -mcpu=v3" go generate ../pkg/datapath/loader
Error: no compiler specified