Add ETL_FORMAT_NO_FLOATING_POINT control macro for etl::format (#1329)

When ETL_FORMAT_NO_FLOATING_POINT is defined, all floating-point formatting support (float, double, long double) is excluded from etl::format. This reduces code size on targets that do not require floating-point formatting.

Guarded sections:

- #include <cmath>

- float/double/long double in supported_format_types variant

- float/double/long double constructors in basic_format_arg

- format_floating_* functions and format_aligned_floating

- formatter<float>, formatter<double>, formatter<long double>

- Floating-point test cases in test_format.cpp

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
Co-authored-by: John Wellbelove <jwellbelove@users.noreply.github.com>

include/etl/format.h

@@ -48,7 +48,9 @@ SOFTWARE.
 #include "variant.h"
 #include "visitor.h"
 
+#if ETL_USING_FORMAT_FLOATING_POINT
 #include <cmath>
+#endif
 
 #if ETL_USING_CPP11
 
@@ -138,9 +140,11 @@ namespace etl
     unsigned int,
     long long int,
     unsigned long long int,
+#if ETL_USING_FORMAT_FLOATING_POINT
     float,
     double,
     long double,
+#endif
     const char*,
     etl::string_view,
     const void*
@@ -302,6 +306,7 @@ namespace etl
     {
     }
 
+#if ETL_USING_FORMAT_FLOATING_POINT
     basic_format_arg(const float v)
     : data(v)
     {
@@ -316,6 +321,7 @@ namespace etl
     : data(v)
     {
     }
+#endif
 
     basic_format_arg(const etl::string_view v)
     : data(v)
@@ -1039,6 +1045,7 @@ namespace etl
       format_plain_num(it, value, spec, width);
     }
 
+#if ETL_USING_FORMAT_FLOATING_POINT
     template<typename OutputIt, typename T>
     void format_floating_default(OutputIt& it, T value, const format_spec_t& spec)
     {
@@ -1214,6 +1221,7 @@ namespace etl
       private_format::format_sequence<OutputIt>(it, ".");
       private_format::format_plain_num<OutputIt, unsigned long long int>(it, fractional_int, spec, fractional_decimals);
     }
+#endif
 
     class dummy_assign_to
     {
@@ -1336,6 +1344,7 @@ namespace etl
       size_t count;
     };
 
+#if ETL_USING_FORMAT_FLOATING_POINT
     template<typename OutputIt, typename T>
     void format_floating_g(OutputIt& it, T value, const format_spec_t& spec)
     {
@@ -1409,6 +1418,7 @@ namespace etl
         }
       }
     }
+#endif
 
     template<class OutputIt>
     struct format_visitor
@@ -1490,6 +1500,7 @@ namespace etl
       return it;
     }
 
+#if ETL_USING_FORMAT_FLOATING_POINT
     template<typename OutputIt, typename Float>
     typename format_context<OutputIt>::iterator format_aligned_floating(Float arg, format_context<OutputIt>& fmt_ctx)
     {
@@ -1534,6 +1545,7 @@ namespace etl
       private_format::fill<OutputIt>(it, suffix_size, fmt_ctx.format_spec.fill);
       return it;
     }
+#endif
 
     template<typename OutputIt>
     void format_string_view(OutputIt& it, etl::string_view arg, const format_spec_t& spec)
@@ -2072,6 +2084,7 @@ namespace etl
     }
   };
 
+#if ETL_USING_FORMAT_FLOATING_POINT
   template<>
   struct formatter<float>
   {
@@ -2119,6 +2132,7 @@ namespace etl
       return private_format::format_aligned_floating<OutputIt, long double>(arg, fmt_ctx);
     }
   };
+#endif
 
   template<>
   struct formatter<etl::string_view>

include/etl/platform.h

@@ -154,6 +154,16 @@ SOFTWARE.
   #define ETL_NOT_USING_WIDE_CHARACTERS 0
 #endif
 
+//*************************************
+// Helper macro for ETL_FORMAT_NO_FLOATING_POINT.
+#if defined(ETL_FORMAT_NO_FLOATING_POINT)
+  #define ETL_USING_FORMAT_FLOATING_POINT     0
+  #define ETL_NOT_USING_FORMAT_FLOATING_POINT 1
+#else
+  #define ETL_USING_FORMAT_FLOATING_POINT     1
+  #define ETL_NOT_USING_FORMAT_FLOATING_POINT 0
+#endif
+
 //*************************************
 // Figure out things about the compiler, if haven't already done so in etl_profile.h
 #include "profiles/determine_compiler_version.h"
@@ -651,6 +661,7 @@ namespace etl
     static ETL_CONSTANT bool using_exceptions                 = (ETL_USING_EXCEPTIONS == 1);
     static ETL_CONSTANT bool using_libc_wchar_h               = (ETL_USING_LIBC_WCHAR_H == 1);
     static ETL_CONSTANT bool using_std_exception              = (ETL_USING_STD_EXCEPTION == 1);
+    static ETL_CONSTANT bool using_format_floating_point      = (ETL_USING_FORMAT_FLOATING_POINT == 1);
     
     // Has...
     static ETL_CONSTANT bool has_initializer_list             = (ETL_HAS_INITIALIZER_LIST == 1);

test/test_format.cpp

@@ -197,6 +197,7 @@ namespace
       CHECK_EQUAL("-6759414", test_format(s, "{}", static_cast<int32_t>(-6759414)));
     }
 
+#if ETL_USING_FORMAT_FLOATING_POINT
     //*************************************************************************
     TEST(test_format_float)
     {
@@ -266,6 +267,7 @@ namespace
       CHECK_EQUAL("0x1.92a738p-5", test_format(s, "{:a}", 0.0000015f));
       CHECK_EQUAL("0x1.6345785d8ap+e", test_format(s, "{:a}", 100000000000000000.l));
     }
+#endif
 
     //*************************************************************************
     TEST(test_format_char_array)