http://llvm.org/bugs/show_bug.cgi?id=10106
Summary: LTO crash possibly related to zero-length arrays
Product: libraries
Version: trunk
Platform: PC
OS/Version: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: Common Code Generator Code
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Created an attachment (id=6714)
--> (http://llvm.org/bugs/attachment.cgi?id=6714)
reduced simplified with bugpoint A.bc
In my code, I've got something like
value = buffer[(writeIndex - 1) & (buflen - 1)];
which if I change to the incorrect
value = buffer[(writeIndex - 1) & buflen];
no longer crashes the code generator. buflen is a constant 32 which gets fed
in, so there's something clever it must be trying to do. In any case, I've
attached the simplified .bc file from running Bugpoint on it. Hopefully that is
of some use.
The structs involved here look like
#define CDC_BUFLEN (32)
struct PSB_Ring_Type
{
uintptr_t ReadIndex, WriteIndex;
uint8_t Buffer[0];
} PACKED_ALIGN(4);
struct PSB_CDC_Side_Type
{
struct PSB_Ring_Type Ring;
uint8_t Buffer[CDC_BUFLEN];
uint32_t BaudRate;
} PACKED_ALIGN(4);
struct PSB_CDC_Type
{
struct PSB_CDC_Side_Type FromMe, ToMe;
} PACKED_ALIGN(4);
I'm thinking it might have something to do with calculating the address of
PSB_Ring_Type's Buffer, or parts of the structure after it. In any case, this
crashes the assembler when LTO is used.
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