Fix: Correctly link C documentation to the C domain (Qiskit#15250) (Qiskit#15252)

Due to the nature of `breathe`, it is assumed all documentation was coming from the c domain because it was coming from a header file with an unspecified language (h files can be either C++ or C). The following commits add an attribute to the "conf.py" file in docs that specifies that files with a ".h" extension are in the C domain.

Co-authored-by: Raynel Sanchez <[email protected]>

Author: mergify[bot]

docs/conf.py

@@ -54,6 +54,9 @@
 
 breathe_projects = {"qiskit": "xml/"}
 breathe_default_project = "qiskit"
+breathe_domain_by_extension = {
+    "h" : "c",
+}
 
 templates_path = ["_templates"]
 

releasenotes/notes/2.2/add-c-standalone-passes-207be980c30c3fe9.yaml

@@ -7,18 +7,18 @@ features_c:
       ==========================================  =============================================================================
       Transpiler pass                             C API Counterpart
       ==========================================  =============================================================================
-      :class:`.BasisTranslator`                   :cpp:func:`qk_transpiler_pass_standalone_basis_translator`
-      :class:`.CommutativeCancellation`           :cpp:func:`qk_transpiler_pass_standalone_commutative_cancellation`
-      :class:`.ConsolidateBlocks`                 :cpp:func:`qk_transpiler_pass_standalone_consolidate_blocks`
-      :class:`.ElidePermutations`                 :cpp:func:`qk_transpiler_pass_standalone_elide_permutations`
-      :class:`.CheckGateDirection`                :cpp:func:`qk_transpiler_pass_standalone_check_gate_direction`
-      :class:`.GateDirection`                     :cpp:func:`qk_transpiler_pass_standalone_gate_direction`
-      :class:`.InverseCancellation`               :cpp:func:`qk_transpiler_pass_standalone_inverse_cancellation`
-      :class:`.Optimize1qGatesDecomposition`      :cpp:func:`qk_transpiler_standalone_optimize_1q_sequences`
-      :class:`.RemoveDiagonalGatesBeforeMeasure`  :cpp:func:`qk_transpiler_pass_standalone_remove_diagonal_gates_before_measure`
-      :class:`.RemoveIdentityEquivalent`          :cpp:func:`qk_transpiler_pass_standalone_remove_identity_equivalent`
-      :class:`.SabreLayout`                       :cpp:func:`qk_transpiler_pass_standalone_sabre_layout`
-      :class:`.Split2QUnitaries`                  :cpp:func:`qk_transpiler_pass_standalone_split_2q_unitaries`
-      :class:`.UnitarySynthesis`                  :cpp:func:`qk_transpiler_pass_standalone_unitary_synthesis`
-      :class:`.VF2Layout`                         :cpp:func:`qk_transpiler_pass_standalone_vf2_layout`
+      :class:`.BasisTranslator`                   :c:func:`qk_transpiler_pass_standalone_basis_translator`
+      :class:`.CommutativeCancellation`           :c:func:`qk_transpiler_pass_standalone_commutative_cancellation`
+      :class:`.ConsolidateBlocks`                 :c:func:`qk_transpiler_pass_standalone_consolidate_blocks`
+      :class:`.ElidePermutations`                 :c:func:`qk_transpiler_pass_standalone_elide_permutations`
+      :class:`.CheckGateDirection`                :c:func:`qk_transpiler_pass_standalone_check_gate_direction`
+      :class:`.GateDirection`                     :c:func:`qk_transpiler_pass_standalone_gate_direction`
+      :class:`.InverseCancellation`               :c:func:`qk_transpiler_pass_standalone_inverse_cancellation`
+      :class:`.Optimize1qGatesDecomposition`      :c:func:`qk_transpiler_standalone_optimize_1q_sequences`
+      :class:`.RemoveDiagonalGatesBeforeMeasure`  :c:func:`qk_transpiler_pass_standalone_remove_diagonal_gates_before_measure`
+      :class:`.RemoveIdentityEquivalent`          :c:func:`qk_transpiler_pass_standalone_remove_identity_equivalent`
+      :class:`.SabreLayout`                       :c:func:`qk_transpiler_pass_standalone_sabre_layout`
+      :class:`.Split2QUnitaries`                  :c:func:`qk_transpiler_pass_standalone_split_2q_unitaries`
+      :class:`.UnitarySynthesis`                  :c:func:`qk_transpiler_pass_standalone_unitary_synthesis`
+      :class:`.VF2Layout`                         :c:func:`qk_transpiler_pass_standalone_vf2_layout`
       ==========================================  =============================================================================

releasenotes/notes/2.2/c-api-ops-count-bug-f633d349de315e89.yaml

@@ -2,5 +2,5 @@
 fixes:
   - |
     Fixed memory leakage issues during the creation of
-    a :cpp:struct:`QkOpCounts` instance and during any calls to
-    :cpp:func:`qk_opcounts_clear` whenever an empty instance is passed.
+    a :c:struct:`QkOpCounts` instance and during any calls to
+    :c:func:`qk_opcounts_clear` whenever an empty instance is passed.

releasenotes/notes/2.2/cbindgen-usize-to-size_t-544294518fdfcbb0.yaml

@@ -3,14 +3,14 @@ upgrade_c:
   - |
     Most usage of `uintptr_t`` has been changed to ``size_t``. Specifically the following usages have been changed:
 
-      * :cpp:member:`QkOpCount::count`
-      * :cpp:member:`QkOpCounts::len`
-      * :cpp:member:`QkObsTerm::len`
-      * The return type of :cpp:func:`qk_circuit_num_instructions`.
-      * The ``index`` argument in :cpp:func:`qk_circuit_get_instruction`.
-      * The ``boundaries`` argument in :cpp:func:`qk_obs_new`.
-      * The return types of :cpp:func:`qk_obs_num_terms`, :cpp:func:`qk_obs_len`, and :cpp:func:`qk_obs_boundaries`.
-      * The return type of :cpp:func:`qk_target_entry_num_properties`, and :cpp:func:`qk_target_num_instructions`.
+      * :c:member:`QkOpCount::count`
+      * :c:member:`QkOpCounts::len`
+      * :c:member:`QkObsTerm::len`
+      * The return type of :c:func:`qk_circuit_num_instructions`.
+      * The ``index`` argument in :c:func:`qk_circuit_get_instruction`.
+      * The ``boundaries`` argument in :c:func:`qk_obs_new`.
+      * The return types of :c:func:`qk_obs_num_terms`, :c:func:`qk_obs_len`, and :c:func:`qk_obs_boundaries`.
+      * The return type of :c:func:`qk_target_entry_num_properties`, and :c:func:`qk_target_num_instructions`.
 
     This change was necessary because the tool used to generate the C header files from Qiskit's rust code,
     `cbindgen <https://github.com/mozilla/cbindgen?tab=readme-ov-file>`__ was using ``uintptr_t`` by default in places

releasenotes/notes/2.2/parameterized_target_c-9c9a4ad2915c2348.yaml

@@ -4,8 +4,8 @@ features_c:
     The ``QkTarget`` type can now represent targets that support
     parameterized ``QkGate`` types that accept any parameter value. Previously,
     these gates could only be added to the target with a fixed angle value
-    supported by using :cpp:func:`qk_target_entry_new_fixed` to create the ``QkTargetEntry``.
-    Now, the :cpp:func:`qk_target_entry_new` function can be used with parameterized gates. 
+    supported by using :c:func:`qk_target_entry_new_fixed` to create the ``QkTargetEntry``.
+    Now, the :c:func:`qk_target_entry_new` function can be used with parameterized gates.
     When it is used with parameterized gates, this function indicates that the gate in the target supports any value for
     all of the gate's parameters. For example:
 

releasenotes/notes/2.2/prepare-2.2.0-99d722b656fba0a8.yaml

@@ -4,7 +4,7 @@ prelude: >
     and bug fixes. The major features of this new release are:
 
       * **C API transpile function:** The C API now includes a function for transpiling a
-        quantum circuit: :cpp:func:`qk_transpile`. This function is equivalent to the Python
+        quantum circuit: :c:func:`qk_transpile`. This function is equivalent to the Python
         :func:`.transpile` function for a standalone C context.
 
       * **Litinski transformation pass:** A new transformation pass :class:`.LitinskiTransformation` that implements

releasenotes/notes/2.2/qk-obs-apply-layot-6d784fa34c18dc1e.yaml

@@ -1,7 +1,7 @@
 ---
 features_c:
   - |
-    Added :cpp:func:`qk_obs_apply_layout` to apply new qubit layouts to a ``QkObs`` observable.
+    Added :c:func:`qk_obs_apply_layout` to apply new qubit layouts to a ``QkObs`` observable.
     This function takes the observable, the new qubit indices, and an output number of qubits.
     Importantly, this function allows applying transpile layouts, usually given as
     ``QkTranspileLayout`` by a transpiler pass, to an observable. For example:

releasenotes/notes/2.2/transpile-c-3d8005b1d67705c9.yaml

@@ -1,7 +1,7 @@
 ---
 features_c:
   - |
-    Added a new function :cpp:func:`qk_transpile` to the Qiskit C API. This function is used for transpiling
+    Added a new function :c:func:`qk_transpile` to the Qiskit C API. This function is used for transpiling
     quantum circuits in a standalone C context without using Python. This is the last major component
     needed in the C API for typical hardware execution workflows using Qiskit.