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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - cfi_startproc should emit a relocation at the actual location of the directive to to match gas(1) behavior"
href="http://llvm.org/bugs/show_bug.cgi?id=19430">19430</a>
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<th>Summary</th>
<td>cfi_startproc should emit a relocation at the actual location of the directive to to match gas(1) behavior
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>MC
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>qcolombet@apple.com
</td>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Currently .cfi_startproc is bound to the last seen symbol.
This was causing a crash when a cfi_startproc was used before any symbol was
defined (see r206236).
Thus, one has to define a symbol before using .cfi_startproc in an assembly
file.
To match gas(1), we should be emit the relocation based on the location of the
directive, not the last symbol.
More information from Eric Christopher <<a href="mailto:echristo@gmail.com">echristo@gmail.com</a>>:
"gas appears to create a symbol for the .cfi_startproc and makes the
relocation relative to it:
.text
.space 1000
.cfi_startproc
.space 1000
.globl _someFunction
_someFunction :
.cfi_def_cfa_offset 16
.cfi_offset %rbp,-16
.cfi_def_cfa_register rbp
ret
.cfi_endproc
RELOCATION RECORDS FOR [.eh_frame]:
OFFSET TYPE VALUE
0000000000000020 R_X86_64_PC32 .text+0x00000000000003e8
which holds up if you do:
.text
.space 1000
.globl _someFunction
_someFunction :
.space 1000
.cfi_startproc
.cfi_def_cfa_offset 16
.cfi_offset %rbp,-16
.cfi_def_cfa_register rbp
ret
.cfi_endproc
RELOCATION RECORDS FOR [.eh_frame]:
OFFSET TYPE VALUE
0000000000000024 R_X86_64_PC32 .text+0x00000000000007d0
which seems to say that to be compatible we'll need to do the
relocation for the .cfi_startproc we need to emit it at the location
of the directive and not at the last known symbol."</pre>
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