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70 lines
2.5 KiB
Diff
70 lines
2.5 KiB
Diff
https://bugs.gentoo.org/936468
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https://github.com/Perl/perl5/issues/22577
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https://github.com/Perl/perl5/pull/22609
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From ffbda81ab95a3db3eff972ad22b633c60365bb8e Mon Sep 17 00:00:00 2001
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From: Tony Cook <tony@develop-help.com>
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Date: Wed, 18 Sep 2024 16:32:34 +1000
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Subject: [PATCH] bodies_by_type[SVt_PVNV]: handle __float128 NV alignment on
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32-bit
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Perl SV body structures include xmg_stash and xmg_u fields at the
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front, which are only valid for type SVt_PVMG and higher.
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This allows those fields to be at a constant offset from the start
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of the body.
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To save memory perl generally allocates the bodies where
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type < SVt_PVMG without the space needed for these two fields,
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offsetting the body pointer back by the size of the two fields. At
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least for the first body in an arena this is technically
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undefined behaviour, but we've done it forever.
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With -msse __float128 requires 16 byte alignment, but for XPVNV
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bodies the hack used here means that the base of the XPVNV
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body ends up mis-aligned on 32-bit systems.
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On 64-bit systems the combined size of those fields is 16-bytes so
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the modified pointer is still properly aligned.
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To fix this allocate the full XPVNV structure when 16 byte alignment
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is required for NV, NV is more than 8 bytes and pointers are small
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enough that the NV would have been mis-aligned.
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Fixes #22577
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---
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sv_inline.h | 15 ++++++++++++++-
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1 file changed, 14 insertions(+), 1 deletion(-)
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diff --git a/sv_inline.h b/sv_inline.h
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index a0fe8ec870c2..7cbca95feef7 100644
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--- a/sv_inline.h
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+++ b/sv_inline.h
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@@ -218,12 +218,25 @@ static const struct body_details bodies_by_type[] = {
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SVt_PVIV, FALSE, NONV, HASARENA,
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FIT_ARENA(0, sizeof(XPVIV) - STRUCT_OFFSET(XPV, xpv_cur)) },
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+#if NVSIZE > 8 && PTRSIZE < 8 && MEM_ALIGNBYTES > 8
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+ /* NV may need strict 16 byte alignment.
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+
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+ On 64-bit systems the NV ends up aligned despite the hack
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+ avoiding allocation of xmg_stash and xmg_u, so only do this
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+ for 32-bit systems.
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+ */
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+ { sizeof(XPVNV),
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+ sizeof(XPVNV),
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+ 0,
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+ SVt_PVNV, FALSE, HADNV, HASARENA,
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+ FIT_ARENA(0, sizeof(XPVNV)) },
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+#else
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{ sizeof(XPVNV) - STRUCT_OFFSET(XPV, xpv_cur),
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copy_length(XPVNV, xnv_u) - STRUCT_OFFSET(XPV, xpv_cur),
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+ STRUCT_OFFSET(XPV, xpv_cur),
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SVt_PVNV, FALSE, HADNV, HASARENA,
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FIT_ARENA(0, sizeof(XPVNV) - STRUCT_OFFSET(XPV, xpv_cur)) },
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-
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+#endif
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{ sizeof(XPVMG), copy_length(XPVMG, xnv_u), 0, SVt_PVMG, FALSE, HADNV,
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HASARENA, FIT_ARENA(0, sizeof(XPVMG)) },
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