LinkOnceODRLinkage on Windows for global variables
I'm compiling two files with clang 6.0: testA.c and testB.c.
On both files I am running a custom compiler pass that inserts a zero-initialized global variable called globalVarTest. I set the linkage of such global variable to be LinkOnceODRLinkage.
Now, when I link testA.c and testB.c together (that is, the object files obtained by compiling them separately), the linker complains that there are multiple definitions of globalVarTest.
Isn't LinkOnceODRLinkage supposed to tell the linker that if both definitions match, the symbols is the same and it can therefore pick any of the two definitions when building the final executable?
UPDATE:
The same procedure works on Linux. Is this a limitation of the Windows linker? I have been able to achieve the same effect using COMDAT sections but I wonder why LLVM is not using that mechanism automatically without me requiring to explicitly set COMDATS.
windows linker llvm
asked Nov 14 '18 at 23:46
BanexBanex
1,52511730
add a comment |
I'm compiling two files with clang 6.0: testA.c and testB.c.
On both files I am running a custom compiler pass that inserts a zero-initialized global variable called globalVarTest. I set the linkage of such global variable to be LinkOnceODRLinkage.
Now, when I link testA.c and testB.c together (that is, the object files obtained by compiling them separately), the linker complains that there are multiple definitions of globalVarTest.
Isn't LinkOnceODRLinkage supposed to tell the linker that if both definitions match, the symbols is the same and it can therefore pick any of the two definitions when building the final executable?
UPDATE:
The same procedure works on Linux. Is this a limitation of the Windows linker? I have been able to achieve the same effect using COMDAT sections but I wonder why LLVM is not using that mechanism automatically without me requiring to explicitly set COMDATS.
windows linker llvm
asked Nov 14 '18 at 23:46
BanexBanex
1,52511730
add a comment |
I'm compiling two files with clang 6.0: testA.c and testB.c.
On both files I am running a custom compiler pass that inserts a zero-initialized global variable called globalVarTest. I set the linkage of such global variable to be LinkOnceODRLinkage.
Now, when I link testA.c and testB.c together (that is, the object files obtained by compiling them separately), the linker complains that there are multiple definitions of globalVarTest.
Isn't LinkOnceODRLinkage supposed to tell the linker that if both definitions match, the symbols is the same and it can therefore pick any of the two definitions when building the final executable?
UPDATE:
The same procedure works on Linux. Is this a limitation of the Windows linker? I have been able to achieve the same effect using COMDAT sections but I wonder why LLVM is not using that mechanism automatically without me requiring to explicitly set COMDATS.
windows linker llvm
asked Nov 14 '18 at 23:46
BanexBanex
1,52511730
I'm compiling two files with clang 6.0: testA.c and testB.c.
On both files I am running a custom compiler pass that inserts a zero-initialized global variable called globalVarTest. I set the linkage of such global variable to be LinkOnceODRLinkage.
Now, when I link testA.c and testB.c together (that is, the object files obtained by compiling them separately), the linker complains that there are multiple definitions of globalVarTest.
Isn't LinkOnceODRLinkage supposed to tell the linker that if both definitions match, the symbols is the same and it can therefore pick any of the two definitions when building the final executable?
UPDATE:
The same procedure works on Linux. Is this a limitation of the Windows linker? I have been able to achieve the same effect using COMDAT sections but I wonder why LLVM is not using that mechanism automatically without me requiring to explicitly set COMDATS.
windows linker llvm
windows linker llvm
asked Nov 14 '18 at 23:46
BanexBanex
1,52511730
asked Nov 14 '18 at 23:46
BanexBanex
1,52511730
edited Nov 16 '18 at 18:02
Banex
asked Nov 14 '18 at 23:46
BanexBanex
1,52511730
asked Nov 14 '18 at 23:46
BanexBanex
1,52511730
asked Nov 14 '18 at 23:46
BanexBanex
1,52511730
1,52511730
add a comment |
add a comment |
1 Answer
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I got an answer from the LLVM mailing list. Using LinkOnceODRLinkage does not work on Windows, even though it used to work in the past.
The best way to achieve the same effect is to explicitly use COMDAT sections. Apparently, this is what was happening automatically by setting LinkOnceODRLinkage, until the behavior changed.
answered Nov 17 '18 at 4:41
BanexBanex
1,52511730
add a comment |
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1 Answer
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I got an answer from the LLVM mailing list. Using LinkOnceODRLinkage does not work on Windows, even though it used to work in the past.
The best way to achieve the same effect is to explicitly use COMDAT sections. Apparently, this is what was happening automatically by setting LinkOnceODRLinkage, until the behavior changed.
answered Nov 17 '18 at 4:41
BanexBanex
1,52511730
add a comment |
I got an answer from the LLVM mailing list. Using LinkOnceODRLinkage does not work on Windows, even though it used to work in the past.
The best way to achieve the same effect is to explicitly use COMDAT sections. Apparently, this is what was happening automatically by setting LinkOnceODRLinkage, until the behavior changed.
answered Nov 17 '18 at 4:41
BanexBanex
1,52511730
add a comment |
I got an answer from the LLVM mailing list. Using LinkOnceODRLinkage does not work on Windows, even though it used to work in the past.
The best way to achieve the same effect is to explicitly use COMDAT sections. Apparently, this is what was happening automatically by setting LinkOnceODRLinkage, until the behavior changed.
answered Nov 17 '18 at 4:41
BanexBanex
1,52511730
I got an answer from the LLVM mailing list. Using LinkOnceODRLinkage does not work on Windows, even though it used to work in the past.
The best way to achieve the same effect is to explicitly use COMDAT sections. Apparently, this is what was happening automatically by setting LinkOnceODRLinkage, until the behavior changed.
answered Nov 17 '18 at 4:41
BanexBanex
1,52511730
answered Nov 17 '18 at 4:41
BanexBanex
1,52511730
answered Nov 17 '18 at 4:41
BanexBanex
1,52511730
answered Nov 17 '18 at 4:41
BanexBanex
1,52511730
1,52511730
add a comment |
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