Re: Implicit case fallthrough warns only when a statement is in place
Andrej Mitrovic: > I did have a bug pop up because I was relying on this new fallthrough > warning system, but it failed to warn me because I didn't have a > statement in one of my cases (I forgot to put a break). -.- This is the consequence of special cases piled on special cases, in the D design. (I agree with Jonathan here). Bye, bearophile
Re: Implicit case fallthrough warns only when a statement is in place
On Monday, November 07, 2011 15:38 Andrej Mitrovic wrote: > import std.stdio; > > void main() > { > int y; > switch (y) > { > case 0: > { > // no warning here on fallthrough > } > > case 1: > { > goto case 2; > } > > case 2: > { > writeln("2"); > break; > } > > default: > } > } > > This won't trigger any warnings when compiled via -w and -wi, and I > think this could be improved. > > DMD will trigger this warning only if you have a statement inside of > 'case 0'. There could be a situation where you forgot to put a break > statement (inside case 0), and you end up in a different case handler > due to the fallthrough to the next case label which has a 'goto' > statement just like above. > > From what I recall of the fallthrough topic, we can either put the > labels together if we really want fallthrough: > > case 0: > case 1: > { > //... > } > > or use "goto case", or an explicit goto: > > case 0: > { > goto case; // or goto case 1; > } > > case 1: > { > //... > } > > IOW, if you have a case defined with braces there should be a warning > on implicit fallthrough. > > I did have a bug pop up because I was relying on this new fallthrough > warning system, but it failed to warn me because I didn't have a > statement in one of my cases (I forgot to put a break). I expect that it's simpler for the compiler to not worry about the braces, since it can just look at the AST without worrying about the tokens. I don't know if Walter would consider it worth changing it for this particular case or not. Just open up an enhancement request. - Jonathan M Davis
Implicit case fallthrough warns only when a statement is in place
import std.stdio; void main() { int y; switch (y) { case 0: { // no warning here on fallthrough } case 1: { goto case 2; } case 2: { writeln("2"); break; } default: } } This won't trigger any warnings when compiled via -w and -wi, and I think this could be improved. DMD will trigger this warning only if you have a statement inside of 'case 0'. There could be a situation where you forgot to put a break statement (inside case 0), and you end up in a different case handler due to the fallthrough to the next case label which has a 'goto' statement just like above. >From what I recall of the fallthrough topic, we can either put the labels together if we really want fallthrough: case 0: case 1: { //... } or use "goto case", or an explicit goto: case 0: { goto case; // or goto case 1; } case 1: { //... } IOW, if you have a case defined with braces there should be a warning on implicit fallthrough. I did have a bug pop up because I was relying on this new fallthrough warning system, but it failed to warn me because I didn't have a statement in one of my cases (I forgot to put a break).