.callgraph Section Layout

The .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 .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.