Hi Linus, On 22 August 2017 at 00:40, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Mon, Aug 21, 2017 at 2:53 PM, Dibyendu Majumdar > <mobile@xxxxxxxxxxxxxxx> wrote: >> >> I notice that the return statement has a symbol associated with - the >> ret_target. What is the meaning of this symbol? > > Sparse uses symbols for branch targets too. > > There's several special target symbols - the return target, the > break/continue targets for loops and switch statements etc. > > For example, a regular label (ie a target of a "goto") is a symbol > with the identifier being the label. Amd the return point is > basically just another label that has the identifier "return". > > So a "return statement" is basically the same as "goto return-label" > (plus the expression handling if there is one, of course). > Okay thanks. > Note that there can be *many* such return points as a function is > generated, since each inlined function will have its return point > pointing to the place in the calling function where it will return. > The same way each 'switch' statement will have its "break" label, and > each "for/.while/do" loop will have it's own "continue" and "break" > labels. > > Note how each label is always described by a symbol, and how you can > look up what "break" means (regardless of whether you're in a switch > or a loop context) by just looking up the "break" label in the > NS_ITERATOR namespace. > > In fact, it should be noted that the code to handle "break" and > "continue" is *EXACTLY*THE*SAME*. That should blow your mind. They > both use exactly the same logic, and they just do exactly the same > thing: look up the symbol associated with that ident, and "goto" it. > Cool. I haven't got around to breaks and continues yet. > (I may be off in some of the details, it's way too long since I looked > at this code). > > The return symbol is also the exit point of a compound statement, so > there's a lot of just commonalities here: any branch target always is > a symbol that is associated with the basic block that is the target. > Okay makes sense. Regards Dibyendu -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
