fix: minor correctness, doc, and include nits

include/CLI/App.hpp

@@ -109,9 +109,8 @@ Option *default_flag_modifiers(Option *opt) {
 
 class Option_group;
 /// Creates a command line program, with very few defaults.
-/** To use, create a new `Program()` instance with `argc`, `argv`, and a help description. The templated
- *  add_option methods make it easy to prepare options. Remember to call `.start` before starting your
- * program, so that the options can be evaluated and the help option doesn't accidentally run your program. */
+/** To use, create a new `App` instance with a description, then call `parse(argc, argv)`. The templated
+ *  add_option methods make it easy to prepare options. After parsing, bound variables hold the parsed values. */
 class App {
     friend Option;
     friend detail::AppFriend;
@@ -411,7 +410,7 @@ class App {
         return this;
     }
 
-    /// Remove the error when extras are left over on the command line.
+    /// Set whether this subcommand/option-group is required to be present on the command line.
     App *required(bool require = true) {
         required_ = require;
         return this;

include/CLI/ExtraValidators.hpp

@@ -562,7 +562,7 @@ inline AsNumberWithUnit::Options operator|(const AsNumberWithUnit::Options &a, c
 /// Converts a human-readable size string (with unit literal) to uin64_t size.
 /// Example:
 ///   "100" => 100
-///   "1 b" => 100
+///   "1 b" => 1
 ///   "10Kb" => 10240 // you can configure this to be interpreted as kilobyte (*1000) or kibibyte (*1024)
 ///   "10 KB" => 10240
 ///   "10 kb" => 10240
@@ -613,7 +613,7 @@ const detail::PermissionValidator ReadPermissions(detail::Permission::read);
 /// Check that the file exist and available for write
 const detail::PermissionValidator WritePermissions(detail::Permission::write);
 
-/// Check that the file exist and available for write
+/// Check that the file exist and available for execute
 const detail::PermissionValidator ExecPermissions(detail::Permission::exec);
 
 /// Check that the file exists and is not empty

include/CLI/Validators.hpp

@@ -281,25 +281,25 @@ class Range : public Validator {
 /// Check for a non negative number
 CLI11_MODULE_INLINE const Range NonNegativeNumber((std::numeric_limits<double>::max)(), "NONNEGATIVE");
 
-/// Check for a positive valued number (val>0.0), <double>::min  here is the smallest positive number
+/// Check for a positive valued number (val>0.0), <double>::denorm_min is the smallest positive number
 CLI11_MODULE_INLINE const
-    Range PositiveNumber((std::numeric_limits<double>::min)(), (std::numeric_limits<double>::max)(), "POSITIVE");
+    Range PositiveNumber((std::numeric_limits<double>::denorm_min)(), (std::numeric_limits<double>::max)(), "POSITIVE");
 
 namespace detail {
 // the following suggestion was made by Nikita Ofitserov(@himikof)
 // done in templates to prevent compiler warnings on negation of unsigned numbers
 
 /// Do a check for overflow on signed numbers
 template <typename T>
-inline typename std::enable_if<std::is_signed<T>::value, T>::type overflowCheck(const T &a, const T &b) {
+inline typename std::enable_if<std::is_signed<T>::value, bool>::type overflowCheck(const T &a, const T &b) {
     if((a > 0) == (b > 0)) {
         return ((std::numeric_limits<T>::max)() / (std::abs)(a) < (std::abs)(b));
     }
     return ((std::numeric_limits<T>::min)() / (std::abs)(a) > -(std::abs)(b));
 }
 /// Do a check for overflow on unsigned numbers
 template <typename T>
-inline typename std::enable_if<!std::is_signed<T>::value, T>::type overflowCheck(const T &a, const T &b) {
+inline typename std::enable_if<!std::is_signed<T>::value, bool>::type overflowCheck(const T &a, const T &b) {
     return ((std::numeric_limits<T>::max)() / a < b);
 }
 

include/CLI/impl/Argv_inl.hpp

@@ -14,7 +14,6 @@
 #include "../Encoding.hpp"
 
 // [CLI11:public_includes:set]
-#include <algorithm>
 #include <memory>
 #include <stdexcept>
 #include <string>

include/CLI/impl/Validators_inl.hpp

@@ -243,7 +243,7 @@ CLI11_INLINE FileOnDefaultPath::FileOnDefaultPath(std::string default_path, bool
         auto path_result = detail::check_path(filename.c_str());
         if(path_result == detail::path_type::nonexistent) {
             std::string test_file_path = default_path;
-            if(default_path.back() != '/' && default_path.back() != '\\') {
+            if(!default_path.empty() && default_path.back() != '/' && default_path.back() != '\\') {
                 // Add folder separator
                 test_file_path += '/';
             }

tests/HelpersTest.cpp

@@ -581,6 +581,12 @@ TEST_CASE("Validators: FilePathModifier", "[helpers]") {
     CLI::FileOnDefaultPath defPathNoFail("../", false);
     CHECK(defPathNoFail(filename2).empty());
     CHECK(filename2 == "nonexistingfile.csv");
+    // empty default path must not invoke UB via back() on an empty string
+    CLI::FileOnDefaultPath defPathEmpty("", false);
+    std::string filename3 = "nonexistingfile.csv";
+    CHECK(defPathEmpty(filename3).empty());
+    CLI::FileOnDefaultPath defPathEmptyErr("", true);
+    CHECK_FALSE(defPathEmptyErr(filename3).empty());
 }
 
 TEST_CASE("Validators: FileIsDir", "[helpers]") {
@@ -647,6 +653,9 @@ TEST_CASE("Validators: PositiveValidator", "[helpers]") {
     CHECK_FALSE(CLI::PositiveNumber(num).empty());
     num = "a";
     CHECK_FALSE(CLI::PositiveNumber(num).empty());
+    // subnormal positive doubles are strictly positive and must be accepted
+    num = "5e-324";  // std::numeric_limits<double>::denorm_min
+    CHECK(CLI::PositiveNumber(num).empty());
 }
 
 TEST_CASE("Validators: NonNegativeValidator", "[helpers]") {