diff mbox series

[bpf-next,3/3] bpftool: turn check on zlib from a phony target into a conditional error

Message ID 20211009210341.6291-4-quentin@isovalent.com (mailing list archive)
State Accepted
Delegated to: BPF
Headers show
Series fixes for bpftool's Makefile | expand

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netdev/fixes_present success Fixes tag not required for -next series
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netdev/tree_selection success Clearly marked for bpf-next
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netdev/cc_maintainers warning 10 maintainers not CCed: irogers@google.com llvm@lists.linux.dev songliubraving@fb.com yhs@fb.com ndesaulniers@google.com john.fastabend@gmail.com kafai@fb.com nathan@kernel.org jean-philippe@linaro.org kpsingh@kernel.org
netdev/source_inline success Was 0 now: 0
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netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success No Fixes tag
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 22 lines checked
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/header_inline success No static functions without inline keyword in header files
bpf/vmtest-bpf-next-PR success PR summary
bpf/vmtest-bpf-next success VM_Test

Commit Message

Quentin Monnet Oct. 9, 2021, 9:03 p.m. UTC 
One of bpftool's object files depends on zlib. To make sure we do not
attempt to build that object when the library is not available, commit
d66fa3c70e59 ("tools: bpftool: add feature check for zlib") introduced a
feature check to detect whether zlib is present.

This check comes as a rule for which the target ("zdep") is a
nonexistent file (phony target), which means that the Makefile always
attempts to rebuild it. It is mostly harmless. However, one side effect
is that, on running again once bpftool is already built, make considers
that "something" (the recipe for zdep) was executed, and does not print
the usual message "make: Nothing to be done for 'all'", which is a
user-friendly indicator that the build went fine.

Before, with some level of debugging information:

    $ make --debug=m
    [...]
    Reading makefiles...

    Auto-detecting system features:
    ...                        libbfd: [ on  ]
    ...        disassembler-four-args: [ on  ]
    ...                          zlib: [ on  ]
    ...                        libcap: [ on  ]
    ...               clang-bpf-co-re: [ on  ]

    Updating makefiles....
    Updating goal targets....
     File 'all' does not exist.
           File 'zdep' does not exist.
          Must remake target 'zdep'.
     File 'all' does not exist.
    Must remake target 'all'.
    Successfully remade target file 'all'.

After the patch:

    $ make --debug=m
    [...]

    Auto-detecting system features:
    ...                        libbfd: [ on  ]
    ...        disassembler-four-args: [ on  ]
    ...                          zlib: [ on  ]
    ...                        libcap: [ on  ]
    ...               clang-bpf-co-re: [ on  ]

    Updating makefiles....
    Updating goal targets....
     File 'all' does not exist.
    Must remake target 'all'.
    Successfully remade target file 'all'.
    make: Nothing to be done for 'all'.

(Note the last line, which is not part of make's debug information.)

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
---
 tools/bpf/bpftool/Makefile | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index 4acec74f459b..2174e21aa57b 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -199,7 +199,10 @@  $(BOOTSTRAP_OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c
 $(OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c
 	$(QUIET_CC)$(CC) $(CFLAGS) -c -MMD -o $@ $<
 
-$(OUTPUT)feature.o: | zdep
+$(OUTPUT)feature.o:
+ifneq ($(feature-zlib), 1)
+	$(error "No zlib found")
+endif
 
 $(BPFTOOL_BOOTSTRAP): $(BOOTSTRAP_OBJS) $(LIBBPF_BOOTSTRAP)
 	$(QUIET_LINK)$(HOSTCC) $(CFLAGS) $(LDFLAGS) -o $@ $(BOOTSTRAP_OBJS) \
@@ -255,10 +258,7 @@  doc-uninstall:
 
 FORCE:
 
-zdep:
-	@if [ "$(feature-zlib)" != "1" ]; then echo "No zlib found"; exit 1 ; fi
-
 .SECONDARY:
-.PHONY: all FORCE clean install-bin install uninstall zdep
+.PHONY: all FORCE clean install-bin install uninstall
 .PHONY: doc doc-clean doc-install doc-uninstall
 .DEFAULT_GOAL := all