File format

gcda/gcno structure (Input of lcov-rs)

These are binary files. Reference

gcda and gcno files follow the same "container" format:

Offset	Size (bytes)	Purpose	Ignored?
0	4	Magic String ("gcda" or "gcno")
4	4	Version
8	4	Stamp (used for "merging")	x
12	*	Contains records

Each file is contained with different types of records.

gcno records

TAG_FUNCTION[0x01000000]

Offset	Size (bytes)	Purpose	Ignored?
0	4	Identifier	x
4	4	Line # Checksum	x
8	4	Config Checksum	x
12	4	Fn Name Length
16	^	Fn Name
?	4	Source Path Length
?	^	Source Path
?	4	Line #

TAG_LINES[0x01450000]

Some exceptions, see gcov header

Offset	Size (bytes)	Purpose	Ignored?
0	4	Block #	x
4	?	Contains multiple lines

Where each line is:

Offset	Size (bytes)	Purpose	Ignored?
0	4	Line #
------	------	If Line # == 0, then changing file:	------
4	4	Next filename's size
8	^	Next filename

lcov "info" file (Output of lcov-rs)

This is a text file. Reference

Prefix	Purpose	Data Format	Strategy
TN	Test Name	String name of test	Leave blank, like lcov is doing in local tests
SF	Source File	Absolute path to source file
FN	Function	line # of fn start, fn name
FNDA	Fn Data	Execution count of fn, fn name
FNF	# Fn Found	integer
FNH	# Fn Executed	integer
DA	Executions for some Line	line #, execution count
LF	# Lines Found	integer
LH	# Lines Executed	integer
end_of_record	End of Record	Signifies end of data for source file	Use the constant "end_of_record"