src: fix gcc/clang warnings

[fanatid]

2 warnings still here. maybe-uninitialized looks like GCC bug. unused-but-set-variable introduced in b53010b#diff-86a9160147028a03800f8ba4fa555285R1502-R1525 -- not sure how should be handled.

PR GCC (9.2.1):

../src/llv8.cc: In member function ‘llnode::v8::Value llnode::v8::JSObject::GetDescriptorProperty(std::string, llnode::v8::Map, llnode::Error&)’:
../src/llv8.cc:1149:14: warning: variable ‘value’ set but not used [-Wunused-but-set-variable]
 1149 |       double value;
      |              ^~~~~
  CXX(target) Release/obj.target/plugin/src/llv8-constants.o
  CXX(target) Release/obj.target/plugin/src/llscan.o
../src/llscan.cc: In member function ‘virtual bool llnode::FindReferencesCmd::DoExecute(lldb::SBDebugger, char**, lldb::SBCommandReturnObject&)’:
../src/llscan.cc:568:22: warning: ‘scanner’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  568 |     ScanForReferences(scanner);
      |     ~~~~~~~~~~~~~~~~~^~~~~~~~~

master GCC (9.2.1):

../src/llv8.cc: In member function ‘double llnode::v8::LLV8::LoadDouble(int64_t, llnode::Error&)’:
../src/llv8.cc:114:11: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
  114 |   return *reinterpret_cast<double*>(&value);
      |           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/llv8.cc: In member function ‘llnode::v8::Value llnode::v8::JSObject::GetDescriptorProperty(std::string, llnode::v8::Map, llnode::Error&)’:
../src/llv8.cc:1149:14: warning: variable ‘value’ set but not used [-Wunused-but-set-variable]
 1149 |       double value;
      |              ^~~~~
../src/llv8.cc: In constructor ‘llnode::v8::StackTrace::StackTrace(llnode::v8::JSArray, llnode::Error&)’:
../src/llv8.cc:1291:74: warning: format ‘%lld’ expects argument of type ‘long long int’, but argument 2 has type ‘int’ [-Wformat=]
 1291 |           "JSArray doesn't look like a Stack Frames array. stack_len: %lld "
      |                                                                       ~~~^
      |                                                                          |
      |                                                                          long long int
      |                                                                       %d
 1292 |           "array_len: %lld",
 1293 |           len_, frame_array_.GetArrayLength(err));
      |           ~~~~                                                            
      |           |
      |           int
../src/llv8.cc:1292:26: warning: format ‘%lld’ expects argument of type ‘long long int’, but argument 3 has type ‘int64_t’ {aka ‘long int’} [-Wformat=]
 1292 |           "array_len: %lld",
      |                       ~~~^
      |                          |
      |                          long long int
      |                       %ld
 1293 |           len_, frame_array_.GetArrayLength(err));
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                                            |
      |                                            int64_t {aka long int}
../src/llscan.cc: In member function ‘virtual bool llnode::FindReferencesCmd::DoExecute(lldb::SBDebugger, char**, lldb::SBCommandReturnObject&)’:
../src/llscan.cc:568:22: warning: ‘scanner’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  568 |     ScanForReferences(scanner);
      |     ~~~~~~~~~~~~~~~~~^~~~~~~~~

master clang (8.0.0):

In file included from ../src/llnode.cc:13:
../src/llnode.h:42:13: warning: private field 'llv8_' is not used [-Wunused-private-field]
  v8::LLV8* llv8_;
            ^
1 warning generated.
../src/llv8.cc:1293:11: warning: format specifies type 'long long' but the argument has type 'int' [-Wformat]
          len_, frame_array_.GetArrayLength(err));
          ^~~~
../src/llv8.cc:1293:17: warning: format specifies type 'long long' but the argument has type 'int64_t' (aka 'long') [-Wformat]
          len_, frame_array_.GetArrayLength(err));
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2 warnings generated.
../src/llscan.cc:650:19: warning: format string is not a string literal (potentially insecure) [-Wformat-security]
    result.Printf(seen_str.str().c_str());
                  ^~~~~~~~~~~~~~~~~~~~~~
../src/llscan.cc:650:19: note: treat the string as an argument to avoid this
    result.Printf(seen_str.str().c_str());
                  ^
                  "%s",
1 warning generated.

[codecov-io]

Codecov Report

Merging #297 into master will increase coverage by 0.61%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #297      +/-   ##
==========================================
+ Coverage   79.23%   79.85%   +0.61%     
==========================================
  Files          33       33              
  Lines        4229     4229              
==========================================
+ Hits         3351     3377      +26     
+ Misses        878      852      -26

Impacted Files	Coverage Δ
src/llnode.cc	74.2% <ø> (ø)	⬆️
src/llnode.h	50% <ø> (ø)	⬆️
src/llscan.cc	61.31% <100%> (ø)	⬆️
src/llv8.cc	75.46% <100%> (+2.46%)	⬆️
src/llv8-constants.cc	83.49% <0%> (+0.97%)	⬆️
src/llv8-inl.h	92.67% <0%> (+1.04%)	⬆️
src/llv8-constants.h	100% <0%> (+1.51%)	⬆️
src/llv8.h	100% <0%> (+2.38%)	⬆️

---

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[mmarchini]

Thanks for looking into it! Overall LGTM.

maybe-uninitialized looks like GCC bug

It does indeed. Maybe there's a better way to write that piece of code which will prevent the warning though? I'll open an issue.

unused-but-set-variable introduced in b53010b#diff-86a9160147028a03800f8ba4fa555285R1502-R1525 -- not sure how should be handled.

That looks wrong... I'm pretty sure I stumbled on this piece of code a few times and didn't change for a reason. I'll open an issue to investigate it further.

[mmarchini]

Landed in 84eefb4, thanks!