[libfuzzer] avoid self-assgin in Command

[yingcong-wu]

Summary

Add test to avoid self-assgin in fuzzer::Command

[yingcong-wu]

Hi all, kindly ping.

[vitalybuka]

Actually in this case self assignment looks like not a problem. If it's so it's recommended not to a check one. string and bool is safe to self assign. Did I miss something?

[yingcong-wu]

Yes, for now, this class is safe to do self-assign. But I think it is best to avoid doing that for it has no benefit doing so.

[vitalybuka]

In D145904#4215399, @yingcong-wu wrote:

Yes, for now, this class is safe to do self-assign. But I think it is best to avoid doing that for it has no benefit doing so.

Here the reasoning. This one is not performance critical, but I don't see a point to break the rule.
https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c62-make-copy-assignment-safe-for-self-assignment

[yingcong-wu]

In D145904#4218381, @vitalybuka wrote:

In D145904#4215399, @yingcong-wu wrote:

Yes, for now, this class is safe to do self-assign. But I think it is best to avoid doing that for it has no benefit doing so.

Here the reasoning. This one is not performance critical, but I don't see a point to break the rule.
https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c62-make-copy-assignment-safe-for-self-assignment

A good & solid reason, I will abandon this patch then.

compiler-rt/lib/fuzzer/FuzzerCommand.h

public:
   explicit Command(const std::vector<std::string> &ArgsToAdd)
       : Args(ArgsToAdd), CombinedOutAndErr(false) {}
 
   explicit Command(const Command &Other)
       : Args(Other.Args), CombinedOutAndErr(Other.CombinedOutAndErr),
         OutputFile(Other.OutputFile) {}
 
   Command &operator=(const Command &Other) {
+    if (&Other != this) {
       Args = Other.Args;
       CombinedOutAndErr = Other.CombinedOutAndErr;
       OutputFile = Other.OutputFile;
+    }
     return *this;
   }
 
   ~Command() {}
 
   // Returns true if the given Arg is present in Args.  Only checks up to
   // "-ignore_remaining_args=1".
   bool hasArgument(const std::string &Arg) const {