http://sourceware.org/bugzilla/show_bug.cgi?id=14727
Bug #: 14727
Summary: --gc-sections deletes section referenced from
.eh_frame
Product: binutils
Version: 2.24 (HEAD)
Status: NEW
Severity: normal
Priority: P2
Component: gold
AssignedTo: i...@airs.com
ReportedBy: amo...@gmail.com
CC: ccout...@google.com
Classification: Unclassified
I see large numbers of failures in the gcc testsuite when ppc32 libstdc++ is
linked with gold. These are all due to the unwinder getting a segfault when
trying to execute a personality function at address 0x7f454c46.
ppc32 uses an eh_frame encoding of 0x9b, DW_EH_PE_indirect | DW_EH_PE_pcrel |
DW_EH_PE_sdata4 for the 'P' augmentation, ie. the personality function. So the
word (four bytes) following the encoding has the relative address of a word
containing the personality function address.
In relocatable object files we have a section in a comdat group
.sdata.DW.ref.__gxx_personality_v0 containing a word with a relocation against
__gxx_personality_v0, the actual personality function. A weak hidden symbol,
DW.ref.__gxx_personality_v0 is defined on this word. The .eh_frame 'P'
augmentation value mentioned above references DW.ref.__gxx_personality_v0.
However, when --gc-sections is enabled *all* .sdata.DW.ref.__gxx_personality_v0
sections are deleted, resulting in DW.ref.__gxx_personality_v0 getting a value
of zero, and the personality function address being loaded from relative
address zero. In a shared object this is the ELF magic number or 0x7f454c46.
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