propane/UPGRADING.md
Josh Holtrop 5fc712c6ee Rework tree generation mode and API
Store tree nodes in congruent, compact arena array.
Define handle types to refer to tree nodes rather than pointers to
structure instances.
Free tree with context.
2026-07-27 20:57:44 -04:00

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## v5.0.0
The generated API for tree generation mode (`tree;`) has been changed
significantly for this version.
The lexer/parser value APIs for non-tree grammars are unchanged.
### Tree memory management
- Remove all calls to `p_tree_delete()` / `p_tree_delete_XXX()`. Tree nodes now
live in the parser context and are freed by `p_context_delete()`.
- Tree node handles (returned by `p_result()` and the field accessors) are only
valid while the context is alive. Do not use them after `p_context_delete()`.
### Tree node field access
Tree nodes are now referenced by handle values instead of pointers, and field
access differs per target language:
- C: replace `node->field` with the accessor function `p_TYPE_field(node)`, or
use the tree walk macro `p_tree_walk_TYPE(node, field1, field2, ...)`. Replace
`x != NULL` / `x == NULL` node checks with `p_node_valid(x)` /
`!p_node_valid(x)`. Read positions with `p_node_position(node)` /
`p_node_end_position(node)`, token payload with `p_TYPE_token(node)` /
`p_TYPE_pvalue(node)` or `p_node_data(node)->field`, and compare node identity
with `p_node_id(a) == p_node_id(b)`.
- C++: replace `node->field` with the handle method `node.field()`. Use
`node.valid()`, `node.position()`, `node.token()`, `node.pvalue()`, and
`node.data()->field` for user token fields. (The C-style functions and macros
above are also available.)
- D: replace pointer declarations (`Start * s`) with value handles (`Start s`)
and replace `x !is null` / `x is null` with `x.valid` / `!x.valid`. Field
access syntax (`node.field.field`) is otherwise unchanged.
### Tree-mode parser rule user code
In tree generation mode `$$` and `$1`, `$2`, ... now expand to node handles.
Reference child fields through the target-language accessors above (for example
`$$->pA->pToken1->pvalue` becomes `p_tree_walk_Start($$, pA, pToken1, pvalue)`
in C, `$$.pA().pToken1().pvalue()` in C++, and `$$.pA.pToken1.pvalue` in D).
## v4.0.0
### API Changes
- Replace any calls to `p_context_init()` with `p_context_new()`.
- Replace any references to the address of a statically allocated context
structure with the pointer returned from `p_context_init()` (e.g. `&context`
-> `context`).
- Add a call to `p_context_delete()` (for C or C++) after lexing/parsing to
reclaim context memory.
- Rename `p_free_tree()` calls to `p_tree_delete()`.
- Change `free_token_node` statement calls from taking a function name argument
to taking a user code block.
## v3.0.0
### Grammar Changes
- Rename `ast;` statement to `tree;`.
- Rename `ast_prefix;` statement to `tree_prefix;`.
- Rename `ast_suffix;` statement to `tree_suffix;`.