Support 'const char**' arguments in Options::parse (#250)

`cxxopts` doesn't modify the contents of the argv strings. This changes
the parse function to take a reference to a `const char**`.

4 files changed, 41 insertions, 40 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4bddcff..16b5a99 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ options. The project adheres to semantic versioning.
 * Fix duplicate default options when there is a short and long option.
 * Add `CXXOPTS_NO_EXCEPTIONS` to disable exceptions.
 * Fix char parsing for space and check for length.
+* Change argument type in `Options::parse` from `char**` to `const char**`.
 
 ## 2.2
 
diff --git a/include/cxxopts.hpp b/include/cxxopts.hpp
index ae95343..995b893 100644
--- a/include/cxxopts.hpp
+++ b/include/cxxopts.hpp
@@ -1211,7 +1211,7 @@ namespace cxxopts
       >,
       std::vector<std::string>,
       bool allow_unrecognised,
-      int&, char**&);
+      int&, const char**&);
 
     size_t
     count(const std::string& o) const
@@ -1251,7 +1251,7 @@ namespace cxxopts
     private:
 
     void
-    parse(int& argc, char**& argv);
+    parse(int& argc, const char**& argv);
 
     void
     add_to_option(const std::string& option, const std::string& arg);
@@ -1274,7 +1274,7 @@ namespace cxxopts
     checked_parse_arg
     (
       int argc,
-      char* argv[],
+      const char* argv[],
       int& current,
       const std::shared_ptr<OptionDetails>& value,
       const std::string& name
@@ -1361,7 +1361,7 @@ namespace cxxopts
     }
 
     ParseResult
-    parse(int& argc, char**& argv);
+    parse(int& argc, const char**& argv);
 
     OptionAdder
     add_options(std::string group = "");
@@ -1620,7 +1620,7 @@ ParseResult::ParseResult
   > options,
   std::vector<std::string> positional,
   bool allow_unrecognised,
-  int& argc, char**& argv
+  int& argc, const char**& argv
 )
 : m_options(std::move(options))
 , m_positional(std::move(positional))
@@ -1734,7 +1734,7 @@ void
 ParseResult::checked_parse_arg
 (
   int argc,
-  char* argv[],
+  const char* argv[],
   int& current,
   const std::shared_ptr<OptionDetails>& value,
   const std::string& name
@@ -1835,7 +1835,7 @@ Options::parse_positional(std::initializer_list<std::string> options)
 
 inline
 ParseResult
-Options::parse(int& argc, char**& argv)
+Options::parse(int& argc, const char**& argv)
 {
   ParseResult result(m_options, m_positional, m_allow_unrecognised, argc, argv);
   return result;
@@ -1843,7 +1843,7 @@ Options::parse(int& argc, char**& argv)
 
 inline
 void
-ParseResult::parse(int& argc, char**& argv)
+ParseResult::parse(int& argc, const char**& argv)
 {
   int current = 1;
 
diff --git a/src/example.cpp b/src/example.cpp
index 9b6ea88..0efb3a4 100644
--- a/src/example.cpp
+++ b/src/example.cpp
@@ -27,7 +27,7 @@ THE SOFTWARE.
 #include "cxxopts.hpp"
 
 void
-parse(int argc, char* argv[])
+parse(int argc, const char* argv[])
 {
   try
   {
@@ -160,7 +160,7 @@ parse(int argc, char* argv[])
   }
 }
 
-int main(int argc, char* argv[])
+int main(int argc, const char* argv[])
 {
   parse(argc, argv);
 
diff --git a/test/options.cpp b/test/options.cpp
index 5026ea0..0dddfe4 100644
--- a/test/options.cpp
+++ b/test/options.cpp
@@ -8,7 +8,7 @@ class Argv {
   public:
 
   Argv(std::initializer_list<const char*> args)
-  : m_argv(new char*[args.size()])
+  : m_argv(new const char*[args.size()])
   , m_argc(static_cast<int>(args.size()))
   {
     int i = 0;
@@ -26,7 +26,7 @@ class Argv {
     }
   }
 
-  char** argv() const {
+  const char** argv() const {
     return m_argv.get();
   }
 
@@ -37,7 +37,7 @@ class Argv {
   private:
 
   std::vector<std::unique_ptr<char[]>> m_args;
-  std::unique_ptr<char*[]> m_argv;
+  std::unique_ptr<const char*[]> m_argv;
   int m_argc;
 };
 
@@ -69,7 +69,7 @@ TEST_CASE("Basic options", "[options]")
     "--space",
   });
 
-  char** actual_argv = argv.argv();
+  auto** actual_argv = argv.argv();
   auto argc = argv.argc();
 
   auto result = options.parse(argc, actual_argv);
@@ -125,7 +125,7 @@ TEST_CASE("No positional", "[positional]")
 
   Argv av({"tester", "a", "b", "def"});
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
   auto result = options.parse(argc, argv);
 
@@ -177,7 +177,7 @@ TEST_CASE("Some positional explicit", "[positional]")
 
   Argv av({"tester", "--output", "a", "b", "c", "d"});
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   auto result = options.parse(argc, argv);
@@ -203,7 +203,7 @@ TEST_CASE("No positional with extras", "[positional]")
 
   Argv av({"extras", "--", "a", "b", "c", "d"});
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   auto old_argv = argv;
@@ -226,7 +226,7 @@ TEST_CASE("Positional not valid", "[positional]") {
 
   Argv av({"foobar", "bar", "baz"});
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   CHECK_THROWS_AS(options.parse(argc, argv), cxxopts::option_not_exists_exception&);
@@ -241,7 +241,7 @@ TEST_CASE("Empty with implicit value", "[implicit]")
 
   Argv av({"implicit", "--implicit="});
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   auto result = options.parse(argc, argv);
@@ -260,7 +260,7 @@ TEST_CASE("Boolean without implicit value", "[implicit]")
   SECTION("When no value provided") {
     Argv av({"no_implicit", "--bool"});
 
-    char** argv = av.argv();
+    auto** argv = av.argv();
     auto argc = av.argc();
 
     CHECK_THROWS_AS(options.parse(argc, argv), cxxopts::missing_argument_exception&);
@@ -269,7 +269,7 @@ TEST_CASE("Boolean without implicit value", "[implicit]")
   SECTION("With equal-separated true") {
     Argv av({"no_implicit", "--bool=true"});
 
-    char** argv = av.argv();
+    auto** argv = av.argv();
     auto argc = av.argc();
 
     auto result = options.parse(argc, argv);
@@ -280,7 +280,7 @@ TEST_CASE("Boolean without implicit value", "[implicit]")
   SECTION("With equal-separated false") {
     Argv av({"no_implicit", "--bool=false"});
 
-    char** argv = av.argv();
+    auto** argv = av.argv();
     auto argc = av.argc();
 
     auto result = options.parse(argc, argv);
@@ -291,7 +291,7 @@ TEST_CASE("Boolean without implicit value", "[implicit]")
   SECTION("With space-separated true") {
     Argv av({"no_implicit", "--bool", "true"});
 
-    char** argv = av.argv();
+    auto** argv = av.argv();
     auto argc = av.argc();
 
     auto result = options.parse(argc, argv);
@@ -302,7 +302,7 @@ TEST_CASE("Boolean without implicit value", "[implicit]")
   SECTION("With space-separated false") {
     Argv av({"no_implicit", "--bool", "false"});
 
-    char** argv = av.argv();
+    auto** argv = av.argv();
     auto argc = av.argc();
 
     auto result = options.parse(argc, argv);
@@ -323,7 +323,7 @@ TEST_CASE("Default values", "[default]")
   SECTION("Sets defaults") {
     Argv av({"implicit"});
 
-    char** argv = av.argv();
+    auto** argv = av.argv();
     auto argc = av.argc();
 
     auto result = options.parse(argc, argv);
@@ -339,7 +339,7 @@ TEST_CASE("Default values", "[default]")
   SECTION("When values provided") {
     Argv av({"implicit", "--default", "5"});
 
-    char** argv = av.argv();
+    auto** argv = av.argv();
     auto argc = av.argc();
 
     auto result = options.parse(argc, argv);
@@ -374,7 +374,7 @@ TEST_CASE("Integers", "[options]")
 
   Argv av({"ints", "--", "5", "6", "-6", "0", "0xab", "0xAf", "0x0"});
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   options.parse_positional("positional");
@@ -401,7 +401,7 @@ TEST_CASE("Leading zero integers", "[options]")
 
   Argv av({"ints", "--", "05", "06", "0x0ab", "0x0001"});
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   options.parse_positional("positional");
@@ -425,7 +425,7 @@ TEST_CASE("Unsigned integers", "[options]")
 
   Argv av({"ints", "--", "-2"});
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   options.parse_positional("positional");
@@ -504,7 +504,7 @@ TEST_CASE("Floats", "[options]")
 
   Argv av({"floats", "--double", "0.5", "--", "4", "-4", "1.5e6", "-1.5e6"});
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   options.parse_positional("positional");
@@ -529,7 +529,7 @@ TEST_CASE("Invalid integers", "[integer]") {
 
     Argv av({"ints", "--", "Ae"});
 
-    char **argv = av.argv();
+    auto** argv = av.argv();
     auto argc = av.argc();
 
     options.parse_positional("positional");
@@ -554,7 +554,7 @@ TEST_CASE("Booleans", "[boolean]") {
 
   Argv av({"booleans", "--bool=false", "--debug=true", "--timing", "--verbose=1", "--dry-run=0", "extra"});
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   auto result = options.parse(argc, argv);
@@ -588,7 +588,7 @@ TEST_CASE("std::vector", "[vector]") {
 
   Argv av({"vector", "--vector", "1,-2.1,3,4.5"});
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   options.parse(argc, argv);
@@ -609,7 +609,7 @@ TEST_CASE("std::optional", "[optional]") {
 
   Argv av({"optional", "--optional", "foo"});
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   options.parse(argc, argv);
@@ -634,7 +634,7 @@ TEST_CASE("Unrecognised options", "[options]") {
     "--another_unknown",
   });
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   SECTION("Default behaviour") {
@@ -661,7 +661,7 @@ TEST_CASE("Allow bad short syntax", "[options]") {
     "-some_bad_short",
   });
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   SECTION("Default behaviour") {
@@ -684,7 +684,7 @@ TEST_CASE("Invalid option syntax", "[options]") {
     "--a",
   });
 
-  char** argv = av.argv();
+  auto** argv = av.argv();
   auto argc = av.argc();
 
   SECTION("Default behaviour") {
@@ -704,7 +704,7 @@ TEST_CASE("Options empty", "[options]") {
        "--unknown"
      });
   auto argc = argv_.argc();
-  char** argv = argv_.argv();
+  auto** argv = argv_.argv();
 
   CHECK(options.groups().empty());
   CHECK_THROWS_AS(options.parse(argc, argv), cxxopts::option_not_exists_exception&);
@@ -733,7 +733,7 @@ TEST_CASE("Initializer list with group", "[options]") {
       "8000",
       "-t",
     });
-  char** actual_argv = argv.argv();
+  auto** actual_argv = argv.argv();
   auto argc = argv.argc();
   auto result = options.parse(argc, actual_argv);
 
@@ -763,7 +763,7 @@ TEST_CASE("Option add with add_option(string, Option)", "[options]") {
        "4"
      });
   auto argc = argv_.argc();
-  char** argv = argv_.argv();
+  auto** argv = argv_.argv();
   auto result = options.parse(argc, argv);
 
   CHECK(result.arguments().size()==2);