Re: [AArch64] nosys.specs and printf

[Tamar Christina <Tamar dot Christina at arm dot com>]

Hi Alex,

It's not that ARM is working, in the sense it does anything useful,

It's just that the warnings don't seem to be emitted because the conftests in libgloss/libnosys/configure.in are too simplistic,
for instance it tests for elf platforms by seeing if the target triple ends with "-elf".

However, just like aarch64, using nosys gives you stubs and not actual code.

/d/t/g/s/gcc (master ↩☡=) ../../build-arm-none-eabi/install/bin/arm-none-eabi-gcc test.c --specs=nosys.specs
/d/t/g/s/gcc (master ↩☡=) ../../build-arm-none-eabi/install/bin/arm-none-eabi-objdump -d a.out

...
0000b0b4 <_lseek>:
    b0b4:	e3a02058 	mov	r2, #88	; 0x58
    b0b8:	e59f3008 	ldr	r3, [pc, #8]	; b0c8 <_lseek+0x14>
    b0bc:	e3e00000 	mvn	r0, #0
    b0c0:	e5832000 	str	r2, [r3]
    b0c4:	e12fff1e 	bx	lr
    b0c8:	0001b9fc 	.word	0x0001b9fc

0000b0cc <_read>:
    b0cc:	e3a02058 	mov	r2, #88	; 0x58
    b0d0:	e59f3008 	ldr	r3, [pc, #8]	; b0e0 <_read+0x14>
    b0d4:	e3e00000 	mvn	r0, #0
    b0d8:	e5832000 	str	r2, [r3]
    b0dc:	e12fff1e 	bx	lr
    b0e0:	0001b9fc 	.word	0x0001b9fc
...

They all just return -1 and set ERRNO just as expected. https://github.com/eblot/newlib/blob/master/libgloss/libnosys/read.c

So Aarch64 is actually working as intended, it's ARM that's missing the warnings. And yeah, in order to suppress the warnings
you need to provide an alternate implementation.

Tamar.
________________________________________
From: Alexander Fedotov <alfedotov@gmail.com>
Sent: Tuesday, September 19, 2017 2:15 PM
To: Tamar Christina
Subject: Re: [AArch64] nosys.specs and printf

Hello Tamar

Well that's sounds to me like newlib completely useless for aarch64 in
current state.
So if I want to use nosys in my way I need to implement empty stubs to
suppress these warnings ? Right ?

How nosys ARM port is working in such case ?

BR,
Alex


On Tue, Sep 19, 2017 at 2:08 PM, Tamar Christina
<Tamar.Christina@arm.com> wrote:
> Hi Alexander,
>
> I believe your changes to libnosys are correct. We don't actually support nosys on AArch64, enough stuff has been committed for particular use cases but that's about it.
>
> The warnings you get with your libnosys changes are correct in that libnosys doesn't provide any IO functionality, so you don't have open, close, read and write. Which means your printf example won't work and it's just warning you ahead of time.
>
> Kind regards,
> Tamar
> ________________________________________
> From: newlib-owner@sourceware.org <newlib-owner@sourceware.org> on behalf of Alexander Fedotov <alfedotov@gmail.com>
> Sent: Friday, September 15, 2017 11:43:23 AM
> To: newlib@sourceware.org
> Subject: [AArch64] nosys.specs and printf
>
> Hello all
>
> I'm trying to compile following simple program for aarch64 with nosys specs
>
> #include <stdio.h>
> int main(void) {
>   printf("hello");
>   return 0;
> }
>
> But I've got:
> d:\gcc-6.3-arm64-eabi\bin>aarch64-none-elf-gcc --specs=nosys.specs test.c
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-sbrkr.o):
> In function `_sbrk_r':
> sbrkr.c:(.text._sbrk_r+0x1c): undefined reference to `_sbrk'
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-writer.o):
> In function `_write_r':
> writer.c:(.text._write_r+0x24): undefined reference to `_write'
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-closer.o):
> In function `_close_r':
> closer.c:(.text._close_r+0x1c): undefined reference to `_close'
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-fstatr.o):
> In function `_fstat_r':
> fstatr.c:(.text._fstat_r+0x20): undefined reference to `_fstat'
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-isattyr.o):
> In function `_isatty_r':
> isattyr.c:(.text._isatty_r+0x1c): undefined reference to `_isatty'
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-lseekr.o):
> In function `_lseek_r':
> lseekr.c:(.text._lseek_r+0x24): undefined reference to `_lseek'
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-readr.o):
> In function `_read_r':
> readr.c:(.text._read_r+0x24): undefined reference to `_read'
> collect2.exe: error: ld returned 1 exit status
>
> d:\gcc-6.3-arm64-eabi\bin>aarch64-none-elf-gcc --specs=rdimon.specs test.c
>
> d:\gcc-6.3-arm64-eabi\bin>
>
>
> I tried to reconfigure libnosys  in the same way as ARM port:
>
> diff -ruN newlib-2.5.0/libgloss/libnosys/configure
> newlib-2.5.0/libgloss/libnosys/configure
> --- newlib-2.5.0/libgloss/libnosys/configure    2016-12-23
> 05:33:54.000000000 +0300
> +++ newlib-2.5.0/libgloss/libnosys/configure    2017-09-15
> 13:14:56.412457618 +0300
> @@ -2009,6 +2009,8 @@
>      ;;
>    a29k-amd-udi)
>      ;;
> +  aarch64*-*-*)
> +    ;;
>    arc-*-*)
>      ;;
>    arm*-*-*)
> diff -ruN newlib-2.5.0/libgloss/libnosys/configure.in
> newlib-2.5.0/libgloss/libnosys/configure.in
> --- newlib-2.5.0/libgloss/libnosys/configure.in    2016-12-23
> 05:33:54.000000000 +0300
> +++ newlib-2.5.0/libgloss/libnosys/configure.in    2017-09-14
> 18:32:27.330466884 +0300
> @@ -43,6 +43,8 @@
>      ;;
>    a29k-amd-udi)
>      ;;
> +  aarch64*-*-*)
> +    ;;
>    arc-*-*)
>      ;;
>    arm*-*-*)
>
> It now compiles so I get final elf, but with warnings:
> d:\gcc-6.3-arm64-eabi\bin>aarch64-none-elf-gcc --specs=nosys.specs test.c
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-closer.o):
> In function `_close_r':
> /home/af/GIT/BG/build_gnu/opt/freescale/Earmv8/obj_newlib/aarch64-none-elf/newlib/libc/reent/../../../../../src_newlib/newlib/libc/reent/closer.c:53:
> warning: _close is not impl
> emented and will always fail
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-fstatr.o):
> In function `_fstat_r':
> /home/af/GIT/BG/build_gnu/opt/freescale/Earmv8/obj_newlib/aarch64-none-elf/newlib/libc/reent/../../../../../src_newlib/newlib/libc/reent/fstatr.c:62:
> warning: _fstat is not impl
> emented and will always fail
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-isattyr.o):
> In function `_isatty_r':
> /home/af/GIT/BG/build_gnu/opt/freescale/Earmv8/obj_newlib/aarch64-none-elf/newlib/libc/reent/../../../../../src_newlib/newlib/libc/reent/isattyr.c:58:
> warning: _isatty is not im
> plemented and will always fail
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-lseekr.o):
> In function `_lseek_r':
> /home/af/GIT/BG/build_gnu/opt/freescale/Earmv8/obj_newlib/aarch64-none-elf/newlib/libc/reent/../../../../../src_newlib/newlib/libc/reent/lseekr.c:58:
> warning: _lseek is not impl
> emented and will always fail
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-readr.o):
> In function `_read_r':
> /home/af/GIT/BG/build_gnu/opt/freescale/Earmv8/obj_newlib/aarch64-none-elf/newlib/libc/reent/../../../../../src_newlib/newlib/libc/reent/readr.c:58:
> warning: _read is not implem
> ented and will always fail
> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-writer.o):
> In function `_write_r':
> /home/af/GIT/BG/build_gnu/opt/freescale/Earmv8/obj_newlib/aarch64-none-elf/newlib/libc/reent/../../../../../src_newlib/newlib/libc/reent/writer.c:58:
> warning: _write is not impl
> emented and will always fail
>
>
> Hi do I correctly to configure AArch64 nosys ?



--
Best regards,
AF