Fix -Wshadow clang warnings

[jschueller]

This fixes some annoying warnings with clang:

/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16411:71: warning: declaration shadows a local variable [-Wshadow]
               static inline std::pair<bool,variable_node_t*> make(T& t,const bool is_const = false)
                                                                      ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16407:67: note: previous declaration is here
         inline bool add(const std::string& symbol_name, RawType& t, const bool is_const = false)
                                                                  ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16411:84: warning: declaration shadows a local variable [-Wshadow]
               static inline std::pair<bool,variable_node_t*> make(T& t,const bool is_const = false)
                                                                                   ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16407:81: note: previous declaration is here
         inline bool add(const std::string& symbol_name, RawType& t, const bool is_const = false)
                                                                                ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16417:82: warning: declaration shadows a local variable [-Wshadow]
               static inline std::pair<bool,stringvar_node_t*> make(std::string& t,const bool is_const = false)
                                                                                 ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16407:67: note: previous declaration is here
         inline bool add(const std::string& symbol_name, RawType& t, const bool is_const = false)
                                                                  ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16417:95: warning: declaration shadows a local variable [-Wshadow]
               static inline std::pair<bool,stringvar_node_t*> make(std::string& t,const bool is_const = false)
                                                                                              ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16407:81: note: previous declaration is here
         inline bool add(const std::string& symbol_name, RawType& t, const bool is_const = false)
                                                                                ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16423:75: warning: declaration shadows a local variable [-Wshadow]
               static inline std::pair<bool,function_t*> make(function_t& t, const bool is_constant = false)
                                                                          ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16407:67: note: previous declaration is here
         inline bool add(const std::string& symbol_name, RawType& t, const bool is_const = false)
                                                                  ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16428:89: warning: declaration shadows a local variable [-Wshadow]
               static inline std::pair<bool,vararg_function_t*> make(vararg_function_t& t, const bool is_const = false)
                                                                                        ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16407:67: note: previous declaration is here
         inline bool add(const std::string& symbol_name, RawType& t, const bool is_const = false)
                                                                  ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16428:103: warning: declaration shadows a local variable [-Wshadow]
               static inline std::pair<bool,vararg_function_t*> make(vararg_function_t& t, const bool is_const = false)
                                                                                                      ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16407:81: note: previous declaration is here
         inline bool add(const std::string& symbol_name, RawType& t, const bool is_const = false)
                                                                                ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16433:91: warning: declaration shadows a local variable [-Wshadow]
               static inline std::pair<bool,generic_function_t*> make(generic_function_t& t, const bool is_constant = false)
                                                                                          ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:16407:67: note: previous declaration is here
         inline bool add(const std::string& symbol_name, RawType& t, const bool is_const = false)
                                                                  ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:23280:55: warning: declaration shadows a local variable [-Wshadow]
                                          std::size_t s, std::size_t e,
                                                      ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:23267:40: note: previous declaration is here
         void split(const std::string& s)
                                       ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:36299:37: warning: declaration shadows a local variable [-Wshadow]
         static inline T process(T& x, T& y, expression<T>& expression)
                                    ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:36251:10: note: previous declaration is here
      T  x = T(0);
         ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:36299:43: warning: declaration shadows a local variable [-Wshadow]
         static inline T process(T& x, T& y, expression<T>& expression)
                                          ^
/home/schueller/projects/openturns/schueller3/lib/src/Base/Func/openturns/exprtk.hpp:36252:10: note: previous declaration is here
      T  y = T(0);

[ArashPartow]

@jschueller Thanks for the PR. I have just tried building exprtk_test with fshadow and I'm not able reproduce those diagnostics.

---

Here is the clang++ output:

~/workspace/exprtk $ make clean exprtk_test
rm -f core.* *~ *.o *.bak *stackdump gmon.out *.gcda *.gcno *.gcnor *.gch
clang++ -pedantic-errors -Wall -Wextra -Werror -Wno-long-long -Wshadow -std=c++17 -O3 -march=native -o exprtk_test exprtk_test.cpp -L/usr/lib -lstdc++ -lm

~/workspace/exprtk $ clang++ --version
clang version 7.0.0 (trunk 326672)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin

---

Here is the g++ output:

~/workspace/exprtk $ make clean exprtk_test
rm -f core.* *~ *.o *.bak *stackdump gmon.out *.gcda *.gcno *.gcnor *.gch
g++-7 -pedantic-errors -Wall -Wextra -Werror -Wno-long-long -Wshadow -std=c++17 -O3 -march=native -o exprtk_test exprtk_test.cpp -L/usr/lib -lstdc++ -lm

~/workspace/exprtk $ g++-7 --version
g++-7 (Ubuntu 7.2.0-1ubuntu1~16.04) 7.2.0
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[jschueller]

Mine is 3.8.0 from ubuntu 16.04:

/usr/bin/clang++ --version
clang version 3.8.0-2ubuntu4 (tags/RELEASE_380/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

[ArashPartow]

The shadow compiler option is very "noisy" when it comes to diagnostics. Have a look at the following talk to get a better idea:

https://www.youtube.com/watch?v=lkgszkPnV8g&f=&t=2377

Since Clang 4, the shadow option has been greatly improved with regards to SNR of its diagnostics. If possible give it a go.

I use the following script to checkout and build the latest version of clang:

https://gist.github.com/anonymous/51ea5545f534b49aaeadce69c3bfbc28

[jschueller]

ok