[Windows] Segmentation fault when returning a struct from a function or instance method #14048
Comments
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assigned to @timurrrr |
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Could you attach the assembly generated by MSVC? |
Please don't attach output generated by the MSVC compiler to the public bug tracker unless you understand all of the implications of its EULA. I don't think we need it for Timur to continue working on this. |
Currently I'm prioritized to get Clang working on Chromium and I don't think the pattern described in this bug is widespread there due to our strict code style. I might be wrong though as we have a lot of third_party/ there. So feel free to take over unless I explicitly take it myself :) |
I'll wager you one beverage of your choice that you end up having to fix this for Chromium. ;] Anyways, prioritize as is convenient for you, I just was pointing out that whomever chooses to dig into this can likely do so w/o someone posting asm. |
Indeed, Chromium's FilePath::DirName returns a FilePath by value, it's a 32-byte structure => boom it crashes. -- Actually it turns out the problem is not that the struct is "2 integers". A similar "returning a struct" scenario works fine for non-class functions or static class method. Changing the subject accordingly. |
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Taking this. After some investigation, there are at least three different problems here:
I have small patches for (1) and (2), but their current versions likely break the Itanium ABI. |
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A fix for everything I know except for __cdecl methods has been committed as r179681. |
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(See also r178291, r178634) |
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Re: cdecl - see llvm/llvm-bugzilla-archive#15768 |
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mentioned in issue llvm/llvm-bugzilla-archive#15556 |
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mentioned in issue llvm/llvm-bugzilla-archive#16226 |
Extended Description
As of r160851,
$ cat with_cl.cpp
struct S {
int a, b;
};
class C {
public:
S foo();
};
S C::foo() {
S ret;
ret.a = 1;
ret.b = 2;
return ret;
}
///////////////////// EOF
$ cat with_clang.cpp
struct S {
int a, b;
};
class C {
public:
S foo();
};
int main() {
C c;
S s = c.foo();
if (s.a != 1)
return 1;
if (s.b != 2)
return 2;
}
///////////////////// EOF
$ clang -Xclang -cxx-abi -Xclang microsoft -c with_clang.cpp && cl -nologo -c with_cl.cpp && link -nologo with_cl.obj with_clang.o
$ with_cl.exe
Segmentation fault
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