http://llvm.org/bugs/show_bug.cgi?id=19012
Bug ID: 19012
Summary: [MS ABI] Bad interaction between inalloca call and
expanded memcpy
Product: clang
Version: unspecified
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Blocks: 12477, 18887
Classification: Unclassified
The following program crashes when built with clang-cl:
(If the #if 1 is changed to #if 0, it doesn't crash. For some reason that
causes us not to expand the memcpy.)
struct Ptr {
~Ptr() {}
int *ptr;
};
#if 1
struct Arr {
struct {
struct {
char name[54];
} mailbox;
int texture_target;
int sync_point;
} mailbox_holder;
void *shared_memory;
struct shared_memory_size {
int width;
int height;
} memory_size;
};
#else
struct Arr {
char x[76];
};
#endif
void f(Ptr) {}
void g(Arr *a, Arr *b, Ptr *p) {
*a = *b; // memcpy, possibly expanded to rep movs, clobbering esi
f(*p); // inalloca call, causing chkstk, not expecting clobbered esi
};
int main() {
Ptr p = {};
Arr a = {}, b = {};
g(&a, &b, &p);
return 0;
}
(Reduced from Chromium's cc::CopyOutputResult::TakeTexture.)
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