Backport #9485: Fix segfault at unpacking modified String

• Status: Closed
• Assignee: usa (Usaku NAKAMURA)

[nobu (Nobuyoshi Nakada)]

trunkではr44803で修正済みですが、1.9.3以降2.1まで ([""].pack("p")<<"a").unpack("p") でSEGVします。
1.9.2までは起きないようです。

[nobu (Nobuyoshi Nakada)]

• Related to Issue #9478 added

[usa (Usaku NAKAMURA)]

• Status changed from Assigned to Closed
• % Done changed from 0 to 100

Applied in changeset r44830.

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merge revision(s) 44803: [Backport #9485]

* string.c (rb_str_modify_expand): enable capacity and disable
  assocation with packed objects when setting capa, so that
  pack("p") string fails to unpack properly after modified.