Re: [PATCH v2 3/4] INSTALL/configure: Update install doc and configure comment

[Leif Lindholm <leif@nuviainc.com>]

On Fri, Apr 10, 2020 at 05:05:48 -0700, Daniel Kiper wrote:
> On Tue, Apr 07, 2020 at 12:16:09PM +0100, Leif Lindholm wrote:
> > On Fri, Apr 03, 2020 at 14:45:02 +0200, Daniel Kiper wrote:
> > > ..to reflect the GRUB build reality in them.
> > >
> > > Additionally, fix ./configure command example formatting in INSTALL file.
> > >
> > > Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
> > > ---
> > >  INSTALL      | 51 +++++++++++++++++++++++++++------------------------
> > >  configure.ac | 10 ++++++----
> > >  2 files changed, 33 insertions(+), 28 deletions(-)
> > >
> > > diff --git a/INSTALL b/INSTALL
> > > index 8acb40902..d1b3bb60e 100644
> > > --- a/INSTALL
> > > +++ b/INSTALL
> > > @@ -160,12 +160,12 @@ For this example the configure line might look like (more details below)
> > >  (some options are optional and included here for completeness but some rarely
> > >  used options are omitted):
> > >
> > > -./configure BUILD_CC=gcc BUILD_PKG_CONFIG=pkg-config --host=amd64-linux-gnu
> > > -CC=amd64-linux-gnu-gcc CFLAGS="-g -O2" PKG_CONFIG=amd64-linux-gnu-pkg-config
> > > ---target=arm --with-platform=uboot TARGET_CC=arm-elf-gcc
> > > -TARGET_CFLAGS="-Os -march=armv6" TARGET_CCASFLAGS="-march=armv6"
> > > -TARGET_OBJCOPY="arm-elf-objcopy" TARGET_STRIP="arm-elf-strip"
> > > -TARGET_NM=arm-elf-nm TARGET_RANLIB=arm-elf-ranlib LEX=gflex
> > > +./configure BUILD_CC=gcc BUILD_PKG_CONFIG=pkg-config --host=amd64-linux-gnu \
> > > +  CC=amd64-linux-gnu-gcc CFLAGS="-g -O2" PKG_CONFIG=amd64-linux-gnu-pkg-config \
> > > +  --target=arm --with-platform=uboot TARGET_CC=arm-elf-gcc \
> > > +  TARGET_CFLAGS="-Os -march=armv6" TARGET_CCASFLAGS="-march=armv6" \
> > > +  TARGET_OBJCOPY="arm-elf-objcopy" TARGET_STRIP="arm-elf-strip" \
> > > +  TARGET_NM=arm-elf-nm TARGET_RANLIB=arm-elf-ranlib LEX=gflex
> >
> > So ... probably should have looked more properly at this round 1.
> >
> > If we are updating this guidance, should we bring it up to date as
> > well?
> >
> > Now we have uefi support in u-boot, the "uboot" platform is the
> > exception rather than the norm. It'd be better to specify
> > --with-platform=efi.
> >
> > Secondly, these appear to be flags used when
> > building GRUB for Raspberry Pi 1; -march-armv6 is quite outdated and
> > could be dropped. (Although I guess it becomes more relevant when seen
> > in combination with TARGET_CCASFLAGS.)
> 
> What do you think about this:
> 
> ./configure --host=x86_64-linux-gnu --target=aarch64-linux-gnu \
>   --with-platform=efi BUILD_CC=gcc BUILD_PKG_CONFIG=pkg-config \
>   HOST_CC=x86_64-linux-gnu-gcc HOST_CFLAGS='-g -O2' \
>   PKG_CONFIG=x86_64-linux-gnu-pkg-config TARGET_CC=aarch64-linux-gnu-gcc \
>   TARGET_CFLAGS='-Os -march=armv8-a' TARGET_CCASFLAGS='-march=armv8-a' \
>   TARGET_OBJCOPY=aarch64-linux-gnu-objcopy \
>   TARGET_STRIP=aarch64-linux-gnu-strip TARGET_NM=aarch64-linux-gnu-nm \
>   TARGET_RANLIB=aarch64-linux-gnu-ranlib LEX=flex

I mean, it's less dated, but it also makes less sense than the
original - an aarch64-linux-gnu-gcc toolchain is very highly likely to
default to -march=armv8-a. It would make more sense to specify
something like -march=armv8.4a.

> > Could we add a sentence here going (if switching to efi for the platform):
> > "Normally, for building a grub on amd64 with tools to run on amd64 to
> > generate images to run on arm, using your Linux distribution's
> > packaged cross compiler, the following would suffice:
> >
> > ./configure --target=arm-linux-gnueabihf --with-platform=efi"
> 
> ./configure --target=aarch64-linux-gnu --with-platform=efi

Again, the original actually made more sense - arm64 only supports efi.

> > >  You need to use following options to specify tools and platforms. For minimum
> > >  version look at prerequisites. All tools not mentioned in this section under
> > > @@ -182,28 +182,31 @@ corresponding platform are not needed for the platform in question.
> > >
> > >    - For host
> > >      1. --host= to autoconf name of host.
> > > -    2. CC= for gcc able to compile for host
> > > -    3. HOST_CFLAGS= for C options for host.
> > > -    4. HOST_CPPFLAGS= for C preprocessor options for host.
> > > -    5. HOST_LDFLAGS= for linker options for host.
> > > -    6. PKG_CONFIG= for pkg-config for host (optional).
> > > -    7. Libdevmapper if any must be in standard linker folders (-ldevmapper) (optional).
> > > -    8. Libfuse if any must be in standard linker folders (-lfuse) (optional).
> > > -    9. Libzfs if any must be in standard linker folders (-lzfs) (optional).
> > > -    10. Liblzma if any must be in standard linker folders (-llzma) (optional).
> > > +    2. CC= for gcc able to compile for host and target.
> >
> > But this is incorrect? Apart from where HOST == TARGET? And goes
> > against the example updated above.
> > Am I missing something?
> 
> It is correct, CC applies for host and target...

So why do we have TARGET_CC and HOST_CC?

My understanding is:
- CC sets the default compilet binary, used for BUILD, HOST and TARGET
  unless overridden for each of these.
- The value of BUILD_CC is used as default for HOST_CC unless
  HOST_CC is explicitly specified.
- The value of HOST_CC is used as the default for TARGET_CC, where *it*
  is not explicitly specified.

Either my understanding here is incorrect, or these changes make the
text more rather than less misleading.

/
    Leif

> > > +    3. CFLAGS= for C options for host and target.
> > > +    4. HOST_CFLAGS= for C options for host.
> > > +    5. HOST_CPPFLAGS= for C preprocessor options for host.
> > > +    6. HOST_LDFLAGS= for linker options for host.
> > > +    7. PKG_CONFIG= for pkg-config for host (optional).
> > > +    8. Libdevmapper if any must be in standard linker folders (-ldevmapper) (optional).
> > > +    9. Libfuse if any must be in standard linker folders (-lfuse) (optional).
> > > +    10. Libzfs if any must be in standard linker folders (-lzfs) (optional).
> > > +    11. Liblzma if any must be in standard linker folders (-llzma) (optional).
> > >
> > >    - For target
> > >      1. --target= to autoconf cpu name of target.
> > >      2. --with-platform to choose firmware.
> > > -    3. TARGET_CC= for gcc able to compile for target
> > > -    4. TARGET_CFLAGS= for C options for target.
> > > -    5. TARGET_CPPFLAGS= for C preprocessor options for target.
> > > -    6. TARGET_CCASFLAGS= for assembler options for target.
> > > -    7. TARGET_LDFLAGS= for linker options for target.
> > > -    8. TARGET_OBJCOPY= for objcopy for target.
> > > -    9. TARGET_STRIP= for strip for target.
> > > -    10. TARGET_NM= for nm for target.
> > > -    11. TARGET_RANLIB= for ranlib for target.
> > > +    3. CC= for gcc able to compile for host and target.
> >
> > Same again.
> 
> Ditto...
> 
> > > +    4. CFLAGS= for C options for host and target.
> > > +    5. TARGET_CC= for gcc able to compile for target.
> > > +    6. TARGET_CFLAGS= for C options for target.
> > > +    7. TARGET_CPPFLAGS= for C preprocessor options for target.
> > > +    8. TARGET_CCASFLAGS= for assembler options for target.
> > > +    9. TARGET_LDFLAGS= for linker options for target.
> > > +    10. TARGET_OBJCOPY= for objcopy for target.
> > > +    11. TARGET_STRIP= for strip for target.
> > > +    12. TARGET_NM= for nm for target.
> > > +    13. TARGET_RANLIB= for ranlib for target.
> > >
> > >    - Additionally for emu, for host and target.
> > >      1. SDL is looked for in standard linker directories (-lSDL) (optional)
> > > diff --git a/configure.ac b/configure.ac
> > > index fc74ee800..06bc4fb0c 100644
> > > --- a/configure.ac
> > > +++ b/configure.ac
> > > @@ -26,10 +26,12 @@ dnl This is necessary because the target type in autoconf does not
> > >  dnl describe such a system very well.
> > >  dnl
> > >  dnl The current strategy is to use variables with no prefix (such as
> > > -dnl CC, CFLAGS, etc.) for the host type, variables with prefix "BUILD_"
> > > -dnl (such as BUILD_CC, BUILD_CFLAGS, etc.) for the build type and variables
> > > -dnl with the prefix "TARGET_" (such as TARGET_CC, TARGET_CFLAGS, etc.) are
> > > -dnl used for the target type. See INSTALL for full list of variables.
> > > +dnl CC, CFLAGS, etc.) for the host and target type, variables with
> >
> > Same again.
> 
> ...and ditto...
> 
> Daniel