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Tue, 25 Jun 2024 10:03:42 +0200 (CEST) From: =?utf-8?q?J=C3=B8rgen_Kvalsvik?= To: gcc-patches@gcc.gnu.org Cc: hubicka@ucw.cz, =?utf-8?q?J=C3=B8rgen_Kvalsvik?= Subject: [PATCH 2/3] Add section on MC/DC in gcov manual Date: Tue, 25 Jun 2024 10:03:31 +0200 Message-Id: <20240625080332.1517736-3-j@lambda.is> In-Reply-To: <20240625080332.1517736-1-j@lambda.is> References: <20240625080332.1517736-1-j@lambda.is> MIME-Version: 1.0 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gcc-patches-bounces+incoming=patchwork.ozlabs.org@gcc.gnu.org gcc/ChangeLog: * doc/gcov.texi: Add MC/DC section. --- gcc/doc/gcov.texi | 72 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) diff --git a/gcc/doc/gcov.texi b/gcc/doc/gcov.texi index dc79bccb8cf..a9221738cce 100644 --- a/gcc/doc/gcov.texi +++ b/gcc/doc/gcov.texi @@ -917,6 +917,78 @@ of times the call was executed will be printed. This will usually be 100%, but may be less for functions that call @code{exit} or @code{longjmp}, and thus may not return every time they are called. +When you use the @option{-g} option, your output looks like this: + +@smallexample +$ gcov -t -m -g tmp + -: 0:Source:tmp.cpp + -: 0:Graph:tmp.gcno + -: 0:Data:tmp.gcda + -: 0:Runs:1 + -: 1:#include + -: 2: + -: 3:int + 1: 4:main (void) + -: 5:@{ + -: 6: int i, total; + 1: 7: total = 0; + -: 8: + 11: 9: for (i = 0; i < 10; i++) +condition outcomes covered 2/2 + 10: 10: total += i; + -: 11: + 1*: 12: int v = total > 100 ? 1 : 2; +condition outcomes covered 1/2 +condition 0 not covered (true) + -: 13: + 1*: 14: if (total != 45 && v == 1) +condition outcomes covered 1/4 +condition 0 not covered (true) +condition 1 not covered (true false) + #####: 15: printf ("Failure\n"); + -: 16: else + 1: 17: printf ("Success\n"); + 1: 18: return 0; + -: 19:@} +@end smallexample + +For every condition the number of taken and total outcomes are +printed, and if there are uncovered outcomes a line will be printed +for each condition showing the uncovered outcome in parentheses. +Conditions are identified by their index -- index 0 is the left-most +condition. In @code{a || (b && c)}, @var{a} is condition 0, @var{b} +condition 1, and @var{c} condition 2. + +An outcome is considered covered if it has an independent effect on +the decision, also known as masking MC/DC (Modified Condition/Decision +Coverage). In this example the decision evaluates to true and @var{a} +is evaluated, but not covered. This is because @var{a} cannot affect +the decision independently -- both @var{a} and @var{b} must change +value for the decision to change. + +@smallexample +$ gcov -t -m -g tmp + -: 0:Source:tmp.c + -: 0:Graph:tmp.gcno + -: 0:Data:tmp.gcda + -: 0:Runs:1 + -: 1:#include + -: 2: + 1: 3:int main() + -: 4:@{ + 1: 5: int a = 1; + 1: 6: int b = 0; + -: 7: + 1: 8: if (a && b) +condition outcomes covered 1/4 +condition 0 not covered (true false) +condition 1 not covered (true) + #####: 9: printf ("Success!\n"); + -: 10: else + 1: 11: printf ("Failure!\n"); + -: 12:@} +@end smallexample + The execution counts are cumulative. If the example program were executed again without removing the @file{.gcda} file, the count for the number of times each line in the source was executed would be added to