Re: [PATCH] Trivial patch to allow bootstrap on MacOS

[Iain Sandoe <idsandoe at googlemail dot com>]

Hello Rainer,

thanks for the patch, but I think it’s only a work-around to part of the  
problem and there are alternate strategies for the “usual case” on  
MacOS/Darwin.

Keller, Rainer <Rainer.Keller@hs-esslingen.de> wrote:

> the following is required to allow bootstrap in libcc1 during stage3 on  
> MacOS Catalina (10.15). libcc1 invokes g++ with —nostdinc++
>
> MacOS Catalina doesn’t provide /usr/include anymore, instead one builds  
> with:
> OSX_SDK_VERSION=`xcodebuild -showsdks | grep 'macOS\ 10' | cut -f2- -d'-'  
> | cut -f2 -d' '`
> OSX_SDK_PATH=`xcodebuild -sdk $OSX_SDK_VERSION -version | grep -E '^Path:  
> ' | cut -f2 -d' '`
>
> configure … --with-build-sysroot=$OSX_SDK_PATH

—with-build-sysroot=  is known to have some problems;

see, for example, https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79885

There is also a current series of patches on the topic from Maciej Rozicki.

I’m not sure what the intent is in using it in the MacOS builds - since I  
expect you will be using the same sysroot (SDK) at run time as you are at  
build time?

====

—with-sysroot= does, however, work (we also now honour SDKROOT in trunk,  
open branches and gcc-7, but not on gcc-6 or gcc-5 [I will probably do some  
Darwin-specific extra patches for the closed branches at some point])

I have sucessfully bootstrapped and tested on Catalina see (for example):

https://gcc.gnu.org/ml/gcc-testresults/2019-11/msg01492.html

Usually, I am using the command line tools, so the installation is not  
going to move….

… however, if you configure with “—with-sysroot=$OSX_SDK_PATH” and then the  
path moves (e.g. you relocate XCode) then you would have to supply the SDK  
position at runtime anyway (either by setting SDKROOT or by passing  
—sysroot=$NEW_SDK_POSITION for each compilation line)

> GMP however is installed elsewhere (by Homebrew, MacPorts etc), so ignore  
> any -nostdinc

it also works to symlink the sources for gmp, mpfr, mpc (and isl, if you  
use it) into the source tree - those then get boostrapped along with the  
compiler and there are no resulting external dependencies (which I find  
preferable).

However, —with-gmp= etc should also work with it (I’ll take a look at that  
case).

> Please note, I am not subscribed to the list.

HTH,
Iain

> Best regards,
> Rainer Keller
>
> gcc/Changelog:
> 	* Have gmp.h be found outside of sysroot
>
> --
> Index: gcc/system.h
> ===================================================================
> --- gcc/system.h        (revision 278783)
> +++ gcc/system.h        (working copy)
> @@ -684,7 +684,7 @@
>
> /* Do not introduce a gmp.h dependency on the build system.  */
> #ifndef GENERATOR_FILE
> -#include <gmp.h>
> +#include "gmp.h"
> #endif
>
> /* Get libiberty declarations.  */