See <https://www.tjhsst.edu/~jcranmer/test-ui/mailnews/mime/src/jsmime.jsm.html>. Notice how each of the branches has only one [ - ] or [ + ] in a bracket? In comparison to stuff like <https://www.tjhsst.edu/~jcranmer/c-ccov/mailnews/compose/src/nsMsgSend.cpp.html>, where a typical two-way branch has a [ - - ] or [ - + ], etc. I haven't tested if switch statements are similarly borked. In essence, this derives from a misunderstanding of the lcov format. In a BRDA line, there are four entries: line number, block number, branch number, count. LCOV is basically a summarization of gcov here, so you need to understand how gcov is instrumenting to see what makes sense. gcov basically builds a control-flow graph, and instruments counters for the targets of the conditional at the end of each basic block if there are more than one entries. The block number is the number of the basic block within the function, and the branch number is the number of the taken edge within the list of possible targets. So, for a normal branch statement, the branch number is 0 for the "true" edge and 1 for the "false" edge (and switch edges number from 0-n for each of the case statements in lexical order, default at end). [Note: I don't know what happens for exceptions, and clang may operate differently there].

(In reply to Joshua Cranmer [:jcranmer] from comment #0) > I haven't tested if switch statements are similarly borked. Note that the semantic of switch statements in JavaScript is literally to iterate on all conditions, as the execution of a case statement expression can have side-effects. So a "case .. expr...:" statement is expected to be equivalent to } else if (x == ...expr...) {

This adds the test cases mentionned in Bug 1209515 (part 6).

As opposed to what I mentionned in comment 1. We do have switch statements which are jumping to multiple targets, and unfortunately, we cannot easily reconstruct the semantic of the original switch case. Thus this code record the jump targets of the table switch statements, and instrument the LCov generation code in order to report the proper output.

Comment on attachment 8683167 [details] [diff] [review] part 3 - SM LCov: Add code coverage support for TableSwitch statements. Review of attachment 8683167 [details] [diff] [review]: ----------------------------------------------------------------- ::: js/src/jsscript.cpp @@ +1338,5 @@ > + > + for (int i = 0; i < high-low+1; i++) { > + pc2 += JUMP_OFFSET_LEN; > + int32_t off = (int32_t) GET_JUMP_OFFSET(pc2); > + if (off != len) { self-nit: s/off != len/off/ (0 is used as a mean to mention the default case)

Note: Landing part 3 is currently blocked Bug 1139235 changes, as we no longer produce line numbers for case statements which have literals.

https://hg.mozilla.org/integration/mozilla-inbound/rev/21f613700470 https://hg.mozilla.org/integration/mozilla-inbound/rev/56e52e58c31f https://hg.mozilla.org/integration/mozilla-inbound/rev/cb9e7ee52f26

https://hg.mozilla.org/mozilla-central/rev/21f613700470 https://hg.mozilla.org/mozilla-central/rev/56e52e58c31f https://hg.mozilla.org/mozilla-central/rev/cb9e7ee52f26