std.debug.StackIterator: account for SPARC %fp quirk

On SPARC, previous %fp is saved with a 14 slots offset from current %fp+bias.
Also account for the bias constant at the new_fp calculation.

1 files changed, 11 insertions, 1 deletions

diff --git a/lib/std/debug.zig b/lib/std/debug.zig
index a434fe0e8b..b887899c7a 100644
--- a/lib/std/debug.zig
+++ b/lib/std/debug.zig
@@ -366,8 +366,18 @@ pub const StackIterator = struct {
         // area, on pretty much every other architecture it points to the stack
         // slot where the previous frame pointer is saved.
         2 * @sizeOf(usize)
+    else if (builtin.arch.isSPARC())
+        // On SPARC the previous frame pointer is stored at 14 slots past %fp+BIAS.
+        14 * @sizeOf(usize)
     else
         0;
+
+    const fp_bias = if (builtin.arch.isSPARC())
+        // On SPARC frame pointers are biased by a constant.
+        2047
+    else
+        0;
+
     // Positive offset of the saved PC wrt the frame pointer.
     const pc_offset = if (builtin.arch == .powerpc64le)
         2 * @sizeOf(usize)
@@ -394,7 +404,7 @@ pub const StackIterator = struct {
         if (fp == 0 or !mem.isAligned(fp, @alignOf(usize)))
             return null;
 
-        const new_fp = @intToPtr(*const usize, fp).*;
+        const new_fp = math.add(usize, @intToPtr(*const usize, fp).*, fp_bias) catch return null;
 
         // Sanity check: the stack grows down thus all the parent frames must be
         // be at addresses that are greater (or equal) than the previous one.