Messages in this thread | | | Date | Tue, 30 Apr 2019 13:04:04 -0400 | From | Rich Felker <> | Subject | Re: Detecting libc in perf (was Re: perf tools build broken after v5.1-rc1) |
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On Tue, Apr 30, 2019 at 03:53:18PM +0000, Vineet Gupta wrote: > 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@quaco 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; > > } > > [acme@quaco linux]$ > > > > [perfbuilder@59ca4b424ded /]$ 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@59ca4b424ded /]$ > > > > Isn't that part of uClibc? > > Right you are. Per the big fat comment right above that code, this gross hack in > uclibc is unavoidable as applications tend to rely on that define. > So a better fix would be to check for various !GLIBC libs explicitly. > > #ifdef __UCLIBC__ > > #elseif defined __MUSL__ > > .... > > Not pretty from app usage pov, but that seems to be the only sane way of doing it.
What are you trying to achieve? I was just CC'd and I'm missing the context.
Rich
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