Re: [PATCH] perf build: Suppress openssl v3 deprecation warnings in libcrypto feature test

[Jiri Olsa <olsajiri@gmail.com>]

On Sat, Jun 25, 2022 at 11:34:38PM +0800, Zixuan Tan wrote:
> With OpenSSL v3 installed, the libcrypto feature check fails as it use the
> deprecated MD5_* API (and is compiled with -Werror). The error message is
> as follows.
> 
> $ make tools/perf
> ```
> Makefile.config:778: No libcrypto.h found, disables jitted code injection,
> please install openssl-devel or libssl-dev
> 
> Auto-detecting system features:
> ...                         dwarf: [ on  ]
> ...            dwarf_getlocations: [ on  ]
> ...                         glibc: [ on  ]
> ...                        libbfd: [ on  ]
> ...                libbfd-buildid: [ on  ]
> ...                        libcap: [ on  ]
> ...                        libelf: [ on  ]
> ...                       libnuma: [ on  ]
> ...        numa_num_possible_cpus: [ on  ]
> ...                       libperl: [ on  ]
> ...                     libpython: [ on  ]
> ...                     libcrypto: [ OFF ]
> ...                     libunwind: [ on  ]
> ...            libdw-dwarf-unwind: [ on  ]
> ...                          zlib: [ on  ]
> ...                          lzma: [ on  ]
> ...                     get_cpuid: [ on  ]
> ...                           bpf: [ on  ]
> ...                        libaio: [ on  ]
> ...                       libzstd: [ on  ]
> ...        disassembler-four-args: [ on  ]
> ```
> 
> This is very confusing because the suggested library (on my Ubuntu 20.04
> it is libssl-dev) is already installed. As the test only checks for the
> presence of libcrypto, this commit suppresses the deprecation warning to
> allow the test to pass.
> 
> Signed-off-by: Zixuan Tan <tanzixuan.me@gmail.com>
> ---
>  tools/build/feature/test-libcrypto.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/tools/build/feature/test-libcrypto.c b/tools/build/feature/test-libcrypto.c
> index a98174e0569c..31afff093d0b 100644
> --- a/tools/build/feature/test-libcrypto.c
> +++ b/tools/build/feature/test-libcrypto.c
> @@ -2,6 +2,12 @@
>  #include <openssl/sha.h>
>  #include <openssl/md5.h>
>  
> +/*
> + * The MD5_* API have been deprecated since OpenSSL 3.0, which causes the
> + * feature test to fail silently. This is a workaround.
> + */

then we use these deprecated MD5 calls in util/genelf.c if libcrypto is detected,
so I wonder how come the rest of the compilation passed for you.. do you have
CONFIG_JITDUMP disabled?

thanks,
jirka

> +#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
> +
>  int main(void)
>  {
>  	MD5_CTX context;
> -- 
> 2.34.1
>