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File format
Mitchell Hentges edited this page Feb 22, 2017
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20 revisions
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.
| Offset | Size (bytes) | Purpose | Ignored? |
|---|---|---|---|
| 0 | 4 | Identifier | |
| 4 | 4 | Line # Checksum | |
| 8 | 4 | Config Checksum | |
| 12 | 4 | Fn Name Length | |
| 16 | ^ | Fn Name | |
| ? | 4 | Source Path Length | |
| ? | ^ | Source Path | |
| ? | 4 | Line # |
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 length | |
| 8 | ^ | Next filename |
| Offset | Size (bytes) | Purpose | Ignored? |
|---|---|---|---|
| 0 | 4 | Number of counters | ? |
| 4 | 4 | Number of program runs | ? |
| 8 | 8 | Sum of all counters accumulated | ? |
| 16 | 8 | Maximum value in single run | ? |
| 24 | 8 | Sum of all runs' maximums | ? |
| 32 | ? | Histogram of counter values | ? |
Note: if this record isn't 3 bytes, it should be ignored. Curiously, the record is commonly not 3 bytes.
| Offset | Size (bytes) | Purpose | Ignored? |
|---|---|---|---|
| 0 | 4 | Identifier | |
| 4 | 4 | Line # Checksum | |
| 8 | 4 | Config Checksum |
Curiously unused when gcov reads gcda files. When in the main parse loop, the closest is a GCOV_TAG_FOR_COUNTER check, (which is based off of TAG_COUNTER_BASE)
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" |