Add script to trim bogus lcov data

There is no (apparent) way to trim branch or line coverage data from
lcov output based on expression matching against the source file.  This
means that we get coverage results that tell us (for example) that we
failed to test lines like 'g_assert_not_reached ();' or didn't test all
branches of a g_assert().

Add a script to read the lcov output and remove line or branch coverage
data according to a list of symbols that are known to have incomplete
coverage when operating as expected.

1 files changed, 53 insertions, 0 deletions

diff --git a/trim-lcov.py b/trim-lcov.py
new file mode 100755
index 0000000..c1709c3
--- /dev/null
+++ b/trim-lcov.py
@@ -0,0 +1,53 @@
+#!/usr/bin/python
+
+# This script removes branch and/or line coverage data for lines that
+# contain a particular substring.
+#
+# In the interest of "fairness" it removes all branch or coverage data
+# when a match is found -- not just negative data.  It is therefore
+# likely that running this script will actually reduce the total number
+# of lines and branches that are marked as covered (in absolute terms).
+#
+# This script intentionally avoids checking for errors.  Any exceptions
+# will trigger make to fail.
+#
+# Author: Ryan Lortie <desrt@desrt.ca>
+
+import sys
+
+line_suppress = ['g_assert_not_reached']
+branch_suppress = ['g_assert', 'g_return_if_fail', 'g_return_val_if_fail', 'G_DEFINE_TYPE']
+
+def check_suppress(suppressions, source, data):
+    line, _, rest = data.partition(',')
+    line = int(line) - 1
+
+    assert line < len(source)
+
+    for suppression in suppressions:
+        if suppression in source[line]:
+            return True
+
+    return False
+
+source = []
+for line in sys.stdin:
+    line = line[:-1]
+
+    keyword, _, rest = line.partition(':')
+
+    # Source file
+    if keyword == 'SF':
+        source = file(rest).readlines()
+
+    # Branch coverage data
+    elif keyword == 'BRDA':
+        if check_suppress(branch_suppress, source, rest):
+            continue
+
+    # Line coverage data
+    elif keyword == 'DA':
+        if check_suppress(line_suppress, source, rest):
+            continue
+
+    print line