> While debugging some gdb-related FAILs, I discovered that gcc's > -fstack-check option effectively calls alloca() to adjust the stack > pointer.
Note that the subject is misleading, -fstack-check is stack checking and not stack protection, which is -fstack-protector. > However, it doesn't mark the stack adjustment as FRAME_RELATED even > when it's setting up the local variables for the function. > > In the case of rx-elf, for this testcase, the CFA for the function is > defined in terms of the stack pointer - and thus is incorrect after > the alloca call. That's the bug, any function using alloca must use the frame pointer as CFA. > My question is: who's fault is this? Should alloca() tell the debug > stuff that the stack pointer has changed? Should it tell it to not > use $sp at all? Should the debug stuff "just know" that $sp isn't a > valid choice for the CFA? Presumably the rx back-end and more precisely TARGET_FRAME_POINTER_REQUIRED, which needs to return true if cfun->calls_alloca. -- Eric Botcazou
