# .llvm.callgraph Section Layout

The `.llvm.callgraph` section is used to store call graph information for each function. The section contains a series of records, with each record corresponding to a single function.

## Per Function Record Layout

Each record in the `.llvm.callgraph` section has the following binary layout:

Field | Type | Size (bits) | Description
--- | --- | --- | ---
Format Version | `uint8_t` | 8 | The version of the record format. The current version is 0.
Flags | `uint8_t` | 8 | A bitfield where: Bit 0 is set if the function is a potential indirect call target; Bit 1 is set if there are direct callees; Bit 2 is set if there are indirect callees. The remaining 5 bits are reserved.
Function Entry PC | `uintptr_t` | 32/64 | The address of the function’s entry point.
Function Type ID | `uint64_t` | 64 | The type ID of the function. This field is non-zero if the function is a potential indirect call target and its type is known.
Number of Unique Direct Callees | `ULEB128` | Variable | The number of unique direct call destinations from this function. This field is only present if there is at least one direct callee.
Direct Callees Array | `uintptr_t[]` | Variable | An array of unique direct callee entry point addresses. This field is only present if there is at least one direct callee.
Number of Unique Indirect Target Type IDs | `ULEB128` | Variable | The number of unique indirect call target type IDs. This field is only present if there is at least one indirect target type ID.
Indirect Target Type IDs Array | `uint64_t[]` | Variable | An array of unique indirect call target type IDs. This field is only present if there is at least one indirect target type ID.