Check zlib feature error

[aguaiyoung]

Makefile.feature may check requirement lib like as zlib,but if clang's version 11.0.0 it's not work well.
some code need escape character like \n you need add like that:

-        $(shell echo $(ZLIB_PROBE) | \
+        $(shell echo -e $(ZLIB_PROBE) | \
       $(CC) $(CFLAGS) -Wall -Werror $(LDFLAGS) -x c - -lz -S -o - >/dev/null 2>&1 \
     && echo 1)

or it output error like that:

<stdin>:1:18: error: extra tokens at end of #include directive [-Werror,-Wextra-tokens]
#include <zlib.h>\n int main(void) {  z_stream zs;      inflateInit(&zs);       return 0; }
                 ^
                 //
1 error generated.

and other echo need echo -e replace

Makefile.include need add EXTRA_WARNINGS in clang version is 11.0.0

      +        -Wno-unused-command-line-argument \

[qmonnet]

Hi, thanks a lot for the report!

Both issues are bugs in the feature detection. It looks that clang does not need the flags telling to the linker what libraries to use, and this results in warnings that break detection due to the use of -Werror. Adding Wno-unused-command-line-argument seems to fix it indeed.

I don't directly experience the issue with the echo on my setup, it “works fine for me”. But echo is not known to be portable, and I'm ready to believe that the current code breaks on other environments. I observed that the $(shell echo) invocation calls /bin/sh (dash for me) which is supposed to use /usr/bin/echo, but it seems that in some cases (including the default case for me, where the current code works), some built-in echo is used instead. I think it's some built-in from make, but didn't manage to confirm it. Anyway. Adding -e is not a solution though: it breaks on my setup. I think we'll switch to using printf instead of echo, hopefully it will be more stable.

If you have a moment, could you please check whether the changes in #5 fix the build on your setup?

[aguaiyoung]

Hi, thanks a lot for the report!

Both issues are bugs in the feature detection. It looks that clang does not need the flags telling to the linker what libraries to use, and this results in warnings that break detection due to the use of -Werror. Adding Wno-unused-command-line-argument seems to fix it indeed.

I don't directly experience the issue with the echo on my setup, it “works fine for me”. But echo is not known to be portable, and I'm ready to believe that the current code breaks on other environments. I observed that the $(shell echo) invocation calls /bin/sh (dash for me) which is supposed to use /usr/bin/echo, but it seems that in some cases (including the default case for me, where the current code works), some built-in echo is used instead. I think it's some built-in from make, but didn't manage to confirm it. Anyway. Adding -e is not a solution though: it breaks on my setup. I think we'll switch to using printf instead of echo, hopefully it will be more stable.

If you have a moment, could you please check whether the changes in #5 fix the build on your setup?

check in my env, it's ok.
thank your replay.
... libbfd: [ on ]
... disassembler-four-args: [ OFF ]
... zlib: [ on ]
... libcap: [ OFF ]
... clang-bpf-co-re: [ on ]

[qmonnet]

And thank you for testing :) Merged now.