On 2/10/21 7:16 AM, Viktor Engelmann wrote:
Am 09.02.2021 um 16:46 schrieb Xi Ruoyao:
On 2021-02-09 16:11 +0100, Viktor Engelmann wrote:
Hello everyone,
I'm building LFS 10.0 on a fully updated Manjaro Linux on an x86_64 for
x86_64.
When I compile M4 (chapter 6.2), I get two errors:
- gcc complains about a void function ("fault_handler") being declared
as "pure" in line 146 of m4.c
- gcc complains about the flag -Wabi which is deprecated and doesn't do
anything
(see the attached log file)
I was able to circumvent the problems by setting the environment variable
CFLAGS=" -fpermissive -Wabi=11 " before ./configure, but I think that
these are infact bugs
in M4, so gcc is rightfully complaining.
It seems that an older gcc version had failed if that function was NOT
declared "pure"
and the M4 team has also discussed this topic in july 2020, see
https://lists.gnu.org/archive/cgi-bin/namazu.cgi?query=fault_handler&submit=Search%21&idxname=bug-m4&max=20&result=normal&sort=score
they had also decided to make the function NOT "pure" (because
fault_handler has sideeffects
and should therefore not be pure). This was implemented by commit
74915227e245c2f93d0db1ff3c53544d8f594dfa in the m4 git repository, but
the declaration
is still present in the .tar.xz from 2016 on http://ftp.gnu.org/gnu/m4/
that is used in LFS.
I verified that LFS and LFS_TGT are set and that I'm compiling with
x86_64-lfs-linux-gnu-gcc.
Everything before M4 was built as regular user.
Those warnings should not be enabled by default.
Is your M4 tarball has the same MD5 checksum in the book? Or did you use some
configure options not mentioned by the book?
Yes, I have compared all the MD5 sums. I followed the book very closely
and I have just compared my scripts to the book again and rebuilt again.
Everything else from chapter 5 and 6 worked fine.
The only thing I can think of that I (might) have done differently is
that I deleted the gcc-10.2.0 directory between building gcc and
libstdc++. The book doesn't explicitly say whether you should do that
Yes it does. Section III, Important Preliminary Material, iii. General
Compilation Instructions, second Important block, item 3e.
and my script deletes target-directories before untaring to prevent
conflicts with previous builds (so the gcc directory is deleted because
libstdc++ is extracted to the same directory as gcc, because it comes
from the same tarball)
In the end, the function /is/ declared as pure and that /is/ logically
wrong, so it's correct of gcc to at least issue a warning. A warning is
also arguable when you pass a deprecated parameter such as -Wabi. It
seems that the warnings are turned into errors because -Werror is also
passed somewhere - I'm still looking into where that happens. But I
would argue that you should use -Werror whenever possible to avoid
unwanted results as much as possible.
-Werror should never be included in released packages. If you don't use
exactly the same tools as the developer, then the odds of a problem rise
significantly. This is is especially true if the developer uses
something like gcc-10.1 and we use gcc-10.2.
-- Bruce
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