Quoting from https://gcc.gnu.org/pipermail/gcc/2021-July/236716.html:
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It was pointed out to me off-list that config/aarch64/value-unwind.h
is missing the runtime exception. It looks like a few other files
are too; a fuller list is:
libgcc/config/aarch64/value-unwind.h
libgcc/config/frv/frv-abi.h
libgcc/config/i386/value-unwind.h
libgcc/config/pa/pa64-hpux-lib.h
Certainly for the aarch64 file this was simply a mistake;
it seems to have been copied from the i386 version, both of which
reference the runtime exception but don't actually include it.
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Similarly, frv-abi.h referenced the exception but didn't include it.
pa64-hpux-lib.h was missing any reference to the exception.
The decision was that this was simply a mistake
[https://gcc.gnu.org/pipermail/gcc/2021-July/236717.html]:
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[…] It generally is
considered a textual omission. The runtime library components of GCC
are intended to be licensed under the runtime exception, which was
granted and approved at the time of introduction.
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and that we should simply change all of the files above
[https://gcc.gnu.org/pipermail/gcc/2021-July/236719.html]:
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Please correct the text in the files. The files in libgcc used in the
GCC runtime are intended to be licensed with the runtime exception and
GCC previously was granted approval for that licensing and purpose.
[…]
The runtime exception explicitly was intended for this purpose and
usage at the time that GCC received approval to apply the exception.
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libgcc/
* config/aarch64/value-unwind.h: Add missing runtime exception
paragraph.
* config/frv/frv-abi.h: Likewise.
* config/i386/value-unwind.h: Likewise.
* config/pa/pa64-hpux-lib.h: Likewise.