On 08/09/2018 08:05 PM, Indu Bhagat wrote: > Wcoverage-mismatch is meant to "Warn in case profiles in -fprofile-use do not > match" > > Currently, gcc compiler warns about the following two cases of source code > changes which alert the programmer to re-generate the profiles : > > 1. Control flow mismatch > If functions' control flow has been altered after profile generation, the > profile count data will not be able to match the cfg_checksum. > Hence the warning, "warning: the control flow of function 'XXX' does not > match its profile data (counter 'YYY') [-Werror=coverage-mismatch]" > > 2. Function is physically moved to a different location > If existing functions are physically swapped in the source file, gcc alerts > the user about potentially stale profiles for all the affected functions. > > Hence the warning, "warning : source locations for function 'XXX' have > changed, the profile data may be out of date [-Werror=coverage-mismatch]" > > So, if new function foo() is added in the source file before existing > functions, gcc alerts the user about potentially stale profiles of the > already seen functions. > Note however, there is no warning about the new function foo(). > Hence, my > proposal #3 below which will cover foo() in this scenario.
Hello. I would appreciate a warning for that. Will you work on a patch or should I do it myself? > > Proposing to add the following cases which are not currently covered : > > 3. If a new function foo() is added to the file. Proposal to add a warning > along > the lines of - > "warning : profile for function ‘XXX’ not found in profile data > [-Wcoverage-mismatch]" > The corner case of foo() being added to the end of the file is > exclusively > covered by #3. > > 4. A new source file is added to the project after profile generation phase. > Proposal to add a warning per function along the lines of - > "warning : profile count data file not found, regenerating profiles may > help [-Wcoverage-mismatch]" I was considering some time ago a warning when a profile is missing for a compilation unit. It's not only situation when a file is added. But one can also wipe somehow .gcda files in make clean and it worth informing a user. I tend to come up with a new warning maybe for it. Again are you planning to work on that? May I please ask you for a bugzilla entry both these issues? Thanks, Martin > > For both #3 and #4, gcc currently does not warn. Although, one can infer that > the count profile data for a specific function / file are missing from the > dump > files, adding warnings #3 and #4 makes the coverage-mismatch set of warnings > more complete for a better end user experience. >
