std.debug: delete MemoryAccessor

This API is based around the unsound idea that a process can perform
checked virtual memory loads to prevent crashing. This depends on
OS-specific APIs that may be unavailable, disabled, or impossible due to
virtualization.

It also makes collecting stack traces ridiculously slow, which is a
problem for users of DebugAllocator - in other words, everybody, all the
time. It also makes strace go from being superbly clean to being awful.

1 files changed, 3 insertions, 10 deletions

diff --git a/lib/std/debug.zig b/lib/std/debug.zig
index ebbcad627b..dd307a0254 100644
--- a/lib/std/debug.zig
+++ b/lib/std/debug.zig
@@ -14,7 +14,6 @@ const native_os = builtin.os.tag;
 const native_endian = native_arch.endian();
 const Writer = std.io.Writer;
 
-pub const MemoryAccessor = @import("debug/MemoryAccessor.zig");
 pub const FixedBufferReader = @import("debug/FixedBufferReader.zig");
 pub const Dwarf = @import("debug/Dwarf.zig");
 pub const Pdb = @import("debug/Pdb.zig");
@@ -773,7 +772,6 @@ pub const StackIterator = struct {
     first_address: ?usize,
     // Last known value of the frame pointer register.
     fp: usize,
-    ma: MemoryAccessor = MemoryAccessor.init,
 
     // When SelfInfo and a register context is available, this iterator can unwind
     // stacks with frames that don't use a frame pointer (ie. -fomit-frame-pointer),
@@ -795,7 +793,7 @@ pub const StackIterator = struct {
                 ::: .{ .memory = true });
         }
 
-        return StackIterator{
+        return .{
             .first_address = first_address,
             // TODO: this is a workaround for #16876
             //.fp = fp orelse @frameAddress(),
@@ -825,7 +823,6 @@ pub const StackIterator = struct {
     }
 
     pub fn deinit(it: *StackIterator) void {
-        it.ma.deinit();
         if (have_ucontext and it.unwind_state != null) it.unwind_state.?.dwarf_context.deinit();
     }
 
@@ -896,7 +893,6 @@ pub const StackIterator = struct {
                         unwind_state.debug_info.allocator,
                         module.base_address,
                         &unwind_state.dwarf_context,
-                        &it.ma,
                         unwind_info,
                         module.eh_frame,
                     )) |return_address| {
@@ -915,7 +911,6 @@ pub const StackIterator = struct {
                 di,
                 module.base_address,
                 &unwind_state.dwarf_context,
-                &it.ma,
                 null,
             );
         } else return error.MissingDebugInfo;
@@ -951,7 +946,7 @@ pub const StackIterator = struct {
 
         // Sanity check.
         if (fp == 0 or !mem.isAligned(fp, @alignOf(usize))) return null;
-        const new_fp = math.add(usize, it.ma.load(usize, fp) orelse return null, fp_bias) catch
+        const new_fp = math.add(usize, @as(*usize, @ptrFromInt(fp)).*, fp_bias) catch
             return null;
 
         // Sanity check: the stack grows down thus all the parent frames must be
@@ -959,8 +954,7 @@ pub const StackIterator = struct {
         // A zero frame pointer often signals this is the last frame, that case
         // is gracefully handled by the next call to next_internal.
         if (new_fp != 0 and new_fp < it.fp) return null;
-        const new_pc = it.ma.load(usize, math.add(usize, fp, pc_offset) catch return null) orelse
-            return null;
+        const new_pc = @as(*usize, @ptrFromInt(math.add(usize, fp, pc_offset) catch return null)).*;
 
         it.fp = new_fp;
 
@@ -1774,7 +1768,6 @@ pub inline fn inValgrind() bool {
 
 test {
     _ = &Dwarf;
-    _ = &MemoryAccessor;
     _ = &FixedBufferReader;
     _ = &Pdb;
     _ = &SelfInfo;