Add GDB formatters for darray and dvec (#10)

- Lets you run `source scripts/gdb/init` in the debugger to pretty-print
dvec and darray types

Author: someone13574

.zed/debug.json

@@ -8,7 +8,7 @@
     },
     "program": "$ZED_WORKTREE_ROOT/build/examples/pdf-example",
     "request": "launch",
-    "adapter": "CodeLLDB"
+    "adapter": "GDB"
   },
   {
     "label": "Debug font-example",
@@ -19,7 +19,7 @@
     },
     "program": "$ZED_WORKTREE_ROOT/build/examples/font-example",
     "request": "launch",
-    "adapter": "CodeLLDB"
+    "adapter": "GDB"
   },
   {
     "label": "Debug tessellation-example",
@@ -30,7 +30,7 @@
     },
     "program": "$ZED_WORKTREE_ROOT/build/examples/tessellation-example",
     "request": "launch",
-    "adapter": "CodeLLDB"
+    "adapter": "GDB"
   },
   {
     "label": "Debug cmap-example",
@@ -41,7 +41,7 @@
     },
     "program": "$ZED_WORKTREE_ROOT/build/examples/cmap-example",
     "request": "launch",
-    "adapter": "CodeLLDB"
+    "adapter": "GDB"
   },
   {
     "label": "Debug test",
@@ -50,11 +50,11 @@
       "args": [],
       "cwd": "$ZED_WORKTREE_ROOT",
       "env": {
-        "DEBUG_TEST_FUNCTION": "test_postscript_tokenize_single_plus_name_non_eof"
+        "DEBUG_TEST_FUNCTION": "test_vec_growth"
       }
     },
     "program": "$ZED_WORKTREE_ROOT/build/libs/test/pdf-test-main",
     "request": "launch",
-    "adapter": "CodeLLDB"
+    "adapter": "GDB"
   }
 ]

libs/arena/include/arena/darray_impl.h

@@ -1,9 +1,12 @@
 #include <stdbool.h>
+#include <stdint.h>
 #include <string.h>
 
 #include "arena/arena.h"
 #include "logger/log.h"
 
+#define DARRAY_DEBUG_MAGIC 0x4152525F444247ULL
+
 // Check arguments
 #ifndef DARRAY_NAME
 #error "DARRAY_NAME is not defined"
@@ -33,6 +36,9 @@ typedef struct DARRAY_NAME DARRAY_NAME;
 struct DARRAY_NAME {
     size_t len;
     DARRAY_TYPE* elements;
+
+    /// Marker field so that the lldb formatter can detect arrays.
+    uint64_t dbg_magic;
 };
 
 // Creates a new arena-backed array of a set size with uninitialized elements
@@ -49,6 +55,7 @@ DARRAY_NAME* DARRAY_FN(new)(Arena* arena, size_t num_elements) {
 
     DARRAY_NAME* array = arena_alloc(arena, sizeof(DARRAY_NAME));
     array->len = num_elements;
+    array->dbg_magic = DARRAY_DEBUG_MAGIC;
 
     if (num_elements != 0) {
         array->elements =
@@ -160,6 +167,7 @@ DARRAY_TYPE* DARRAY_FN(get_raw)(const DARRAY_NAME* array, size_t* len_out) {
 }
 
 // Undefines
+#undef DARRAY_DEBUG_MAGIC
 #undef DARRAY_NAME
 #undef DARRAY_LOWERCASE_NAME
 #undef DARRAY_TYPE

libs/arena/include/arena/dvec_impl.h

@@ -1,8 +1,11 @@
 #include <stdbool.h>
+#include <stdint.h>
 
 #include "arena/arena.h"
 #include "logger/log.h"
 
+#define DVEC_DEBUG_MAGIC 0x5645435F444247ULL
+
 #ifndef DVEC_SRC
 #define DVEC_SRC
 #ifdef _MSC_VER
@@ -60,6 +63,9 @@ struct DVEC_NAME {
     size_t len;
     size_t allocated_blocks;
     DVEC_TYPE* blocks[DVEC_MAX_BLOCKS];
+
+    /// Marker field so that the lldb formatter can detect vecs.
+    uint64_t dbg_magic;
 };
 
 // Creates a new arena-backed vector with zero elements
@@ -77,6 +83,7 @@ DVEC_NAME* DVEC_FN(new)(Arena* arena) {
     vec->len = 0;
     vec->allocated_blocks = 0;
     vec->blocks[0] = NULL;
+    vec->dbg_magic = DVEC_DEBUG_MAGIC;
 
     return vec;
 }
@@ -223,6 +230,7 @@ size_t DVEC_FN(len)(const DVEC_NAME* vec) {
 }
 
 // Undefines
+#undef DVEC_DEBUG_MAGIC
 #undef DVEC_NAME
 #undef DVEC_LOWERCASE_NAME
 #undef DVEC_TYPE

scripts/gdb/.gitignore

@@ -0,0 +1 @@
+__pycache__

scripts/gdb/darray_gdb.py

@@ -0,0 +1,66 @@
+import gdb
+import fmt_helpers
+
+DARRAY_DEBUG_MAGIC = 0x4152525F444247
+
+
+class DArrayPrinter:
+    def __init__(self, val):
+        self.val = fmt_helpers.strip_ptr_and_typedefs(val)
+
+        try:
+            self.length = int(self.val["len"])
+        except Exception:
+            self.length = 0
+
+        try:
+            self.elements = self.val["elements"]
+        except Exception:
+            self.elements = None
+
+    def to_string(self):
+        return f"darray[{self.length}]"
+
+    def children(self):
+        if not self.elements:
+            return
+
+        try:
+            element_type = self.elements.type
+
+            if self.length < 0:
+                return
+            for idx in range(self.length):
+                try:
+                    yield ("[%d]" % idx, self.elements[idx])
+                except Exception:
+                    yield ("[%d]" % idx, "<error reading element>")
+        except Exception:
+            return
+
+    def display_hint(self):
+        return "array"
+
+
+def darray_printer_lookup(val):
+    try:
+        candidate = fmt_helpers.strip_ptr_and_typedefs(val)
+        magic_field = candidate["dbg_magic"]
+        magic = int(magic_field)
+    except Exception:
+        return None
+
+    if magic == DARRAY_DEBUG_MAGIC:
+        return DArrayPrinter(val)
+
+    return None
+
+
+def register_darray_printers(objfile=None):
+    if objfile is None:
+        gdb.pretty_printers.append(darray_printer_lookup)
+    else:
+        gdb.printing.register_pretty_printer_for_object_file(objfile, darray_printer_lookup)
+
+
+register_darray_printers()

scripts/gdb/dvec_gdb.py

@@ -0,0 +1,78 @@
+import gdb
+import fmt_helpers
+import math
+
+DVEC_DEBUG_MAGIC = 0x5645435F444247
+
+
+class DVecPrinter:
+    def __init__(self, val):
+        self.val = fmt_helpers.strip_ptr_and_typedefs(val)
+
+        try:
+            self.length = int(self.val["len"])
+        except Exception:
+            self.length = 0
+
+        try:
+            self.num_blocks = int(self.val["allocated_blocks"])
+        except Exception:
+            self.num_blocks = 0
+
+        try:
+            self.blocks = self.val["blocks"]
+        except Exception:
+            self.blocks = None
+
+    def to_string(self):
+        return f"dvec[{self.length}] ({self.num_blocks} blocks)"
+
+    def children(self):
+        if not self.blocks:
+            return
+
+        try:
+            block_type = self.blocks.type
+
+            if self.length < 0:
+                return
+            for idx in range(self.length):
+                block_idx = math.floor(math.log2(idx + 1))
+                idx_in_block = idx - (2**block_idx - 1)
+
+                if block_idx >= self.num_blocks or idx < 0:
+                    yield (f"[{idx}]", "shit")
+                else:
+                    try:
+                        yield (f"[{idx}]", self.blocks[block_idx][idx_in_block])
+                    except Exception:
+                        yield (f"[{idx}]", "<error reading element>")
+        except Exception:
+            return
+
+    def display_hint(self):
+        return "array"
+
+
+def dvec_printer_lookup(val):
+    try:
+        candidate = fmt_helpers.strip_ptr_and_typedefs(val)
+        magic_field = candidate["dbg_magic"]
+        magic = int(magic_field)
+    except Exception:
+        return None
+
+    if magic == DVEC_DEBUG_MAGIC:
+        return DVecPrinter(val)
+
+    return None
+
+
+def register_dvec_printers(objfile=None):
+    if objfile is None:
+        gdb.pretty_printers.append(dvec_printer_lookup)
+    else:
+        gdb.printing.register_pretty_printer_for_object_file(objfile, dvec_printer_lookup)
+
+
+register_dvec_printers()

scripts/gdb/fmt_helpers.py

@@ -0,0 +1,20 @@
+import gdb
+
+def strip_ptr_and_typedefs(val):
+    """Helper function to remove pointers, qualifiers and typedefs from a value"""
+    typ = val.type
+
+    # Strips typedefs and qualifiers
+    try:
+        typ = typ.strip_typedefs()
+    except Exception:
+        pass
+
+    # Deference pointers
+    if typ.code == gdb.TYPE_CODE_PTR:
+        try:
+            return val.dereference()
+        except gdb.error:
+            # Return original value if deference fails (ie. due to NULL)
+            return val
+    return val

scripts/gdb/init

@@ -0,0 +1,6 @@
+python
+import sys, os
+sys.path.insert(0, os.path.join(os.getcwd(), "scripts", "gdb"))
+import darray_gdb
+import dvec_gdb
+end