# Build fix: remove `boost_system` from CMake components
`Boost.System` became header-only in Boost 1.69. Boost 1.90.0 no longer ships a compiled library or CMake config for it, so `find_package(Boost REQUIRED COMPONENTS system ...)` fails.
## Fix
`cmake/CMakeLists.txt`:
```diff
- set(BOOST_COMPONENTS system program_options regex thread date_time iostreams)
The headers are still available; no linking is needed.
# Build fix: add `template` keyword for dependent template member calls
Calling a template member function through a dependent expression (e.g. `storage->has_attribute_value<T>(...)` where `storage`'s type depends on a template parameter) requires the `template` keyword to disambiguate from a less-than comparison.
## Error
```
src/ifcparse/IfcParse.cpp:1856:67: error: expected primary-expression before '>' token
1856 | if (storage->has_attribute_value<express::Base>(attr_index)) {
| ^
```
Six identical errors at lines 1856, 1865, 1896, 1905, 1934, 1943.
Applied at all six call sites in `in_memory_file_storage::read_from_stream`.
# Linker fix: missing explicit template instantiations for `InstanceStreamer`
`InstanceStreamer` is a class template with methods defined in `IfcParse.cpp`, not the header. Without explicit instantiations, the linker can't find the symbols when the SWIG wrapper loads.
Cannot use `template class InstanceStreamer<...>` because some constructors have `static_assert` guards that reject certain reader types. Instead, instantiate each member function individually per reader type, only including the constructors valid for that type.
`src/ifcparse/IfcParse.cpp` (after the last `InstanceStreamer` method definition):
SWIG's `stream_from_string` calls `InstanceStreamer<FileReader<FullBufferImpl>>(void*, int, IfcFile*)`, but the `(void*, int)` constructor previously hit a `static_assert` for `FullBufferImpl` — it only allowed `PushedSequentialImpl`.
# Runtime fix: segfault in `parse_context::push()` due to vector reallocation
`parse_context_pool` stores nodes in a `std::vector<parse_context>`. During parsing, `load()` takes a `parse_context&` parameter and calls `context.push()`, which calls `pool_->make()`. If the pool's vector reallocates (via `emplace_back`), all existing references into the vector — including the `context` reference held by the caller — become dangling. Subsequent access through the dangling reference causes a segfault.
Triggered by larger IFC files (e.g. `ISSUE_159_kleine_Wohnung_R22.ifc`, 9.5 MB) that cause enough pool growth to trigger reallocation.
## Error
```
Thread 1 received signal SIGSEGV, Segmentation fault.
0x... in IfcParse::parse_context::push()
#1 in_memory_file_storage::load(...) // context& is dangling after reallocation
`src/ifcparse/storage.h` — change the pool container from `std::vector` to `std::deque`, which does not invalidate references on `push_back`/`emplace_back`:
```diff
+#include <deque>
struct parse_context_pool {
- std::vector<parse_context> nodes_;
+ std::deque<parse_context> nodes_;
```
# Runtime fix: `express::Base` comparison operators throw on null/expired instances
`express::Base::operator<` and `operator==` called `data()`, which throws `std::runtime_error("Trying to access deleted instance reference")` when the internal `weak_ptr` is expired. A default-constructed `express::Base` (the value-type equivalent of a null pointer) always has an expired `weak_ptr`.
## Why this model triggers it
The bug requires two conditions to coincide:
1. A representation is shared by **more than one product** (via `IfcRepresentationMap` / `IfcMappedItem`).
2. At least one of those products has **no material association**, so `get_single_material_association()` returns `express::Base{}` (the null equivalent).
In `advanced_model.ifc`, Body representations like `#449` (Body/Brep) have a single `IfcRepresentationMap` (`#453`) with 13 `IfcMappedItem` usages, meaning 13 products share the geometry. Some of those products (e.g. `IfcFlowTerminal` instances) have no `IfcRelAssociatesMaterial`, so `get_single_material_association` returns `express::Base{}`.
Smaller or simpler models don't hit this because either:
- Every representation maps to only 1 product → `reuse_ok_` short-circuits at `products.size() == 1` before reaching the material check.
- Every product has a material association → no null `express::Base` is ever inserted into the set.
→ reps contains only the 143 Axis tasks created before the throw
→ all 143 Axis reps have Curve2D geometry → map(representation) returns null
→ no valid elements produced → initialize() returns false
```
In the old pointer-based code, `reuse_ok_` used `std::set<const IfcUtil::IfcBaseEntity*>` and `get_single_material_association` returned `nullptr`. Inserting `nullptr` into a `std::set<T*>` is a plain pointer comparison — no dereference, no throw. The refactoring to `std::set<express::Base>` changed the comparison from pointer comparison to `express::Base::operator<`, which unconditionally dereferences through `data()`.
## Error
```
[Error] Trying to access deleted instance reference
[Notice] Created 143 tasks for 143 products ← only Axis reps; all Body reps lost
initialize() returned: False
```
## Fix
`src/ifcparse/express.h` — use `weak_ptr::lock().get()` instead of `data()` so that expired pointers compare as `nullptr` (matching old raw-pointer semantics):
```diff
bool operator<(const Base& other) const {
- return data() < other.data();
+ auto a = data_.lock();
+ auto b = other.data_.lock();
+ return a.get() < b.get();
}
bool operator==(const Base& other) const {
- return data() == other.data();
+ auto a = data_.lock();
+ auto b = other.data_.lock();
+ return a.get() == b.get();
}
```
# Runtime fix: `entity_instance` missing `get_inverse` due to SWIG `%rename` collision
Accessing inverse attributes (e.g. `element.IsDecomposedBy`) on any entity raises `AttributeError: entity instance of type 'IFC2X3.IfcProject' has no attribute 'get_inverse'`.
## Why
`entity_instance_mixin.__getattr__` (line 106 of `entity_instance.py`) calls `self.get_inverse(name)` when it detects an inverse attribute. Since the mixin inherits into the SWIG-generated `entity_instance` class (via the `object = custom_base` hack in `IfcParseWrapper.i:936`), `self.get_inverse` must resolve to a method on the SWIG class.
However, `IfcParseWrapper.i:70` has a global rename:
This was intended for `ifcopenshell::file::get_inverse` (which takes an entity + declaration and returns instances by reference), but SWIG `%rename` is global — it also renames the `%extend express::Base` method `get_inverse(const std::string& a)` at line 551. So the Python-side `entity_instance` class exposes the method as `get_inverses_by_declaration`, not `get_inverse`.
The old code (`v0.8.0`) didn't hit this because `__getattr__` called `self.wrapped_data.get_inverse(name)` on an inner `ifcopenshell_wrapper.entity_instance` object — but in that old layout, the inner object was constructed differently and the rename didn't apply the same way (or the method had a different path). In the new mixin approach, `self`**is** the SWIG object, so the rename is directly visible.
## Fix
`src/ifcwrap/IfcParseWrapper.i` — override the global rename specifically for `express::Base::get_inverse`, restoring the original name on entity instances:
Add this line **before** the global rename (or anywhere before the `%extend express::Base` block). This scoped rename takes precedence for `express::Base`, so:
-`entity_instance.get_inverse(name)` works as the mixin expects
-`file.get_inverses_by_declaration(...)` keeps its intended name
## Python-side workaround
`entity_instance.py:106` — call the method by its SWIG-renamed name:
```diff
- vs = self.get_inverse(name)
+ vs = self.get_inverses_by_declaration(name)
```
# Runtime fix: `entity_instance` class no longer importable from `entity_instance` module
The class rename from `entity_instance` to `entity_instance_mixin` broke external code that does `from ifcopenshell.entity_instance import entity_instance`.
## Error
```
ImportError: cannot import name 'entity_instance' from 'ifcopenshell.entity_instance'
```
Triggered at import time via `ifcopenshell.util.pset` (and likely other modules).
## Fix
`src/ifcopenshell-python/ifcopenshell/entity_instance.py` — add a backwards-compatible alias at the bottom of the module:
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Dion Moult