#3260: Linking stage2 on PPC gives "scattered reloc r_address too large"
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Reporter: benl | Owner:
Type: bug | Status: new
Priority: normal | Milestone: _|_
Component: Compiler | Version: 6.13
Keywords: | Difficulty: Unknown
Os: MacOS X | Testcase:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Comment(by PHO):
> Does anyone know why Mach-O has this limit on segment sizes for .o
files, but not for shared libraries?
I think I can explain this.
First of all, I have to apologize that my previous explanation was
inaccurate.
1. The size limitation applies to sections, not segments.
2. ld(1) complains about sections larger than 2^24^ - 1 bytes ''if and
only if'' there exists a scattered relocation entry whose r_address points
to such sections.
Look at the load commands of libHSghc-*.dylib. This dylib actually has a
large section:
{{{
% otool -l
compiler/stage2/build/libHSghc-6.13.20100516-ghc6.13.20100516.dylib
compiler/stage2/build/libHSghc-6.13.20100516-ghc6.13.20100516.dylib:
Load command 0
cmd LC_SEGMENT
cmdsize 260
segname __TEXT
vmaddr 0x00000000
vmsize 0x0181d000
fileoff 0
filesize 25284608
maxprot 0x00000007
initprot 0x00000005
nsects 3
flags 0x0
Section
sectname __text
segname __TEXT
addr 0x00001240
size 0x01701fbc // <- Larger than 2^24 - 1 bytes!
offset 4672
align 2^4 (16)
reloff 0
nreloc 0
flags 0x80000400
reserved1 0
reserved2 0
...
}}}
But since dynamic libraries are position-independent, every references
to external segments (or external libraries) are indirectly referred
using symbol pointers. Since symbol pointers are located in the same
segment at which the referring !__text section is located, no scattered
relocations are needed for them. Thus it's not really a problem to
have large sections for dynamic libraries.
{{{
% otool -rv
compiler/stage2/build/libHSghc-6.13.20100516-ghc6.13.20100516.dylib | awk
'{print $5}' | sort | uniq
VANILLA // <- There are no relocation entries with types other than
VANILLA.
entries
type
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3260#comment:13>
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