Re: [patch/rfa/hppa] Use frame pointer for unwinding

Andrew Cagney
2004-05-17T15:23:00Z

+ /* Check to see if a frame pointer is available, and use it for
+ frame unwinding if it is.
+
+ There are some situations where we need to rely on the frame
+ pointer to do stack unwinding. For example, if a function calls
+ alloca (), the stack pointer can get adjusted inside the body of
+ the function. In this case, the ABI requires that the compiler
+ maintain a frame pointer for the function.
+
+ The unwind record has a flag (alloca_frame) that indicates that
+ a function has a variable frame; unfortunately, gcc/binutils
+ does not set this flag. Instead, whenever a frame pointer is used
+ and saved on the stack, the Save_SP flag is set. We use this to
+ decide whether to use the frame pointer for unwinding. */
+
+ fp = frame_unwind_register_unsigned (next_frame, HPPA_FP_REGNUM);
+
+ if (frame_pc_unwind (next_frame) >= prologue_end
+ && u->Save_SP && fp != 0)
fp will effectively always be non-zero here, so the ``fp != 0'' is a
just-in-case? Suggest adding that, and the GCC bug-number, as additions
to the comments.

+ {
+ cache->base = fp;
+
+ if (hppa_debug)
+ fprintf_unfiltered (gdb_stdlog, " (base=0x%s) [frame pointer] }",
+ paddr_nz (cache->base));
+ }
+ else if (frame_pc_unwind (next_frame) >= prologue_end)
otherwize ok

Andrew