[LLVMdev] [llvm] [libunwind] r207467 misprint

[Nick Kledzik]

Daniil,

It looks like those asserts were added by Dan Albert.

225187  danalbert       assert((int)CFI_Parser<A>::kMaxRegisterNumber > lastReg &&
225187  danalbert              "register range too large");
225187  danalbert       assert(lastReg <= (int)cieInfo.returnAddressRegister &&
225187  danalbert              "register range does not contain return address register");

The assert for the return register is complicated because stack based calling conventions (like x86[_64]) don’t have a register for the return value.  Instead the dwarf makes up a number (x86 uses 8) for the return address number.  This assert happens to work as-is for x86[_64] because the return register number == lastReg.  

-Nick


> On Jul 14, 2015, at 4:45 AM, Daniil Troshkov <troshkovdanil at gmail.com> wrote:
> 
> Hi Nick!
>  
> In r207467 you added code(libunwind: DwarfInstructions.hpp):
>  
>       assert(lastReg <= (int)cieInfo.returnAddressRegister
>                  && "register range does not contain return address register");
>       for (int i = 0; i <= lastReg; ++i) {
> .....
>           else if (i == (int)cieInfo.returnAddressRegister)
>  
> There is misprint here: lastReg should be >= (int)cieInfo.returnAddressRegister in assert.
>  
> So patch is:
>  
> Index: DwarfInstructions.hpp
> ===================================================================
> --- DwarfInstructions.hpp (revision 242137)
> +++ DwarfInstructions.hpp (working copy)
> @@ -170,7 +170,7 @@
>        const int lastReg = R::lastDwarfRegNum();
>        assert((int)CFI_Parser<A>::kMaxRegisterNumber > lastReg &&
>               "register range too large");
> -      assert(lastReg <= (int)cieInfo.returnAddressRegister &&
> +      assert(lastReg >= (int)cieInfo.returnAddressRegister &&
>               "register range does not contain return address register");
>        for (int i = 0; i <= lastReg; ++i) {
>          if (prolog.savedRegisters[i].location !=
> If you agree, can you please commit it, because I have no commit access.
>  
> Thank you!
> <DwarfInstructions.hpp.patch>

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