linux-kernel - Re: perf tools build broken after v5.1-rc1

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Date:   Thu, 2 May 2019 09:53:56 -0700
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
CC:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
        lkml <linux-kernel@...r.kernel.org>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        "Namhyung Kim" <namhyung@...nel.org>,
        arcml <linux-snps-arc@...ts.infradead.org>
Subject: Re: perf tools build broken after v5.1-rc1

On 4/29/19 6:18 PM, Arnaldo Carvalho de Melo wrote:
>>>
>>> Auto-detecting system features:
>>> ...                         dwarf: [ OFF ]
>>> ...            dwarf_getlocations: [ OFF ]
>>> ...                         glibc: [ on  ]
>>
>> Not related to current issue, this run uses a uClibc toolchain and yet it is
>> detecting glibc - doesn't seem right to me.
> 
> Ok, I'll improve that, I think it just tries to detect a libc, yeah,
> see:
> 
> [acme@...co linux]$ cat tools/build/feature/test-glibc.c
> // SPDX-License-Identifier: GPL-2.0
> #include <stdlib.h>
> 
> #if !defined(__UCLIBC__)
> #include <gnu/libc-version.h>
> #else
> #define XSTR(s) STR(s)
> #define STR(s) #s
> #endif
> 
> int main(void)
> {
> #if !defined(__UCLIBC__)
> 	const char *version = gnu_get_libc_version();
> #else
> 	const char *version = XSTR(__GLIBC__) "." XSTR(__GLIBC_MINOR__);
> #endif
> 
> 	return (long)version;
> }

So we return a pointer to a string to declare a glibc build ?
But won't it do so even for other libs, even if those numbers were 0:0. I'm
confused how this feature detction works.

> [acme@...co linux]$
> 
> [perfbuilder@...a4b424ded /]$ grep __GLIBC__ /arc_gnu_2017.09-rc2_prebuilt_uclibc_le_arc700_linux_install/arc-snps-linux-uclibc/sysroot/usr/include/*.h
> /arc_gnu_2017.09-rc2_prebuilt_uclibc_le_arc700_linux_install/arc-snps-linux-uclibc/sysroot/usr/include/features.h:   The macros `__GNU_LIBRARY__', `__GLIBC__', and `__GLIBC_MINOR__' are
> /arc_gnu_2017.09-rc2_prebuilt_uclibc_le_arc700_linux_install/arc-snps-linux-uclibc/sysroot/usr/include/features.h:#define	__GLIBC__	2
> /arc_gnu_2017.09-rc2_prebuilt_uclibc_le_arc700_linux_install/arc-snps-linux-uclibc/sysroot/usr/include/features.h:	((__GLIBC__ << 16) + __GLIBC_MINOR__ >= ((maj) << 16) + (min))
> [perfbuilder@...a4b424ded /]$
> 
> Isn't that part of uClibc?