An alternative proposed by Fred which is an OK middle ground IMHO is that of not inserting a decl for the unmangled name, but treat this symbol always as-it-is. i.e. if we have a symbol _Znwm in some object, we don't insert a decl for `operator new(unsigned long)` but for _Znwm itself.
Greg, Jason, would that work for you guys? Thanks! -- Davide On Tue, Mar 13, 2018 at 10:25 AM, Davide Italiano <dccitali...@gmail.com> wrote: > On Tue, Mar 13, 2018 at 9:59 AM, Frédéric Riss via lldb-commits > <lldb-commits@lists.llvm.org> wrote: >> >> >>> On Mar 12, 2018, at 6:40 PM, Davide Italiano via lldb-commits >>> <lldb-commits@lists.llvm.org> wrote: >>> >>> Author: davide >>> Date: Mon Mar 12 18:40:00 2018 >>> New Revision: 327356 >>> >>> URL: http://llvm.org/viewvc/llvm-project?rev=327356&view=rev >>> Log: >>> [ExpressionParser] Fix crash when evaluating invalid expresssions. >>> >>> Typical example, illformed comparisons (operator== where LHS and >>> RHS are not compatible). If a symbol matched `operator==` in any >>> of the object files lldb inserted a generic function declaration >>> in the ASTContext on which Sema operates. Maintaining the AST >>> context invariants is fairly tricky and sometimes resulted in >>> crashes inside clang (or assertions hit). >>> >>> The real reason why this feature exists in the first place is >>> that of allowing users to do something like: >>> (lldb) call printf("patatino") >>> >>> even if the debug informations for printf() is not available. >>> Eventually, we might reconsider this feature in its >>> entirety, but for now we can't remove it as it would break >>> a bunch of users. Instead, try to limit it to non-C++ symbols, >>> where getting the invariants right is hopefully easier. >>> >>> Now you can't do in lldb anymore >>> (lldb) call _Zsomethingsomething(1,2,3) >>> >>> but that doesn't seem to be such a big loss. >> >> I’m somewhat surprised by this. My understanding of the crash you were >> investigating is that Clang crashed because we injected a Decl looking like >> this: “void operator==(…)” after finding the operator== symbol somewhere. I >> think injecting bogus C++ Decls makes no sense and it cannot really work >> anyway. >> >> On the other hand, I see no harm in injecting “_Zsomethingsomething(…)” as a >> C Decl. This can be useful, and people should be able to call raw symbols in >> their binaries. Is there no way to keep the later while preventing the >> creation of broken C++ decls? >> > > Thank you all for your feedback. I'll reply with a single mail to everybody. > > C decls can be inserted. In fact, this works, even after my changes: > > (lldb) call printf("patatino") > (int) $0 = 8 > > I always thought identifiers beginning with underscore where illegal in C. > Here's what the standard says: > > http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf > > Section 7.1.3 > "All identifiers that begin with an underscore and either an uppercase > letter or another underscore are always reserved for any use." > > They're not quite illegal, but they're reserved, so I'm unsure how > frequent having symbols starting with `_Z` is popular. > > Maybe lldb has a better way of detecting whether this is a C or a C++ program? > > There are several constraints: > > 1) The object from which we're loading symbols has no debug info, so > we can't look at the CU and just say whether it's C or C++ or > Objective-C. > 2) The expression parser always evaluates expressions in a C++ context > (to the best of my understanding) > 3) You can always mix-and-match C/C++ object files as they're just > Mach-O or ELF objects at that point (not recommended, but I've seen > people doing it). > > Do you have any thoughts on how this should be achieved? > > Best, > > -- > Davide _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
