Fix clang -Wfloat-equal warning

CMakeLists.txt

@@ -47,6 +47,7 @@ if (ENABLE_CUSTOM_COMPILER_FLAGS)
             -Wmissing-variable-declarations
             -Wused-but-marked-unused
             -Wswitch-enum
+            -Wfloat-equal
         )
     elseif("${CMAKE_C_COMPILER_ID}" STREQUAL "MSVC")
         # Disable warning c4001 - nonstandard extension 'single line comment' was used

Makefile

@@ -37,7 +37,7 @@ else
 endif
 
 PIC_FLAGS = -fPIC
-R_CFLAGS = $(PIC_FLAGS) -pedantic -Wall -Werror -Wstrict-prototypes -Wwrite-strings -Wshadow -Winit-self -Wcast-align -Wformat=2 -Wmissing-prototypes -Wstrict-overflow=2 -Wcast-qual -Wc++-compat -Wundef -Wswitch-default -Wconversion $(CFLAGS)
+R_CFLAGS = -fPIC -std=c89 -pedantic -Wall -Werror -Wstrict-prototypes -Wwrite-strings -Wshadow -Winit-self -Wcast-align -Wformat=2 -Wmissing-prototypes -Wstrict-overflow=2 -Wcast-qual -Wc++-compat -Wundef -Wswitch-default -Wconversion -Wfloat-equal $(CFLAGS)
 
 uname := $(shell sh -c 'uname -s 2>/dev/null || echo false')
 

cJSON.c

@@ -480,6 +480,12 @@ static void update_offset(printbuffer * const buffer)
     buffer->offset += strlen((const char*)buffer_pointer);
 }
 
+/* securely comparison of floating-point variables */
+static cJSON_bool compare_double(double a, double b)
+{
+    return (fabs(a - b) <= a * CJSON_DOUBLE_PRECIION);
+}
+
 /* Render the number nicely from the given item into a string. */
 static cJSON_bool print_number(const cJSON * const item, printbuffer * const output_buffer)
 {
@@ -497,7 +503,7 @@ static cJSON_bool print_number(const cJSON * const item, printbuffer * const out
     }
 
     /* This checks for NaN and Infinity */
-    if ((d * 0) != 0)
+    if (!compare_double(d * 0, 0))
     {
         length = sprintf((char*)number_buffer, "null");
     }
@@ -507,7 +513,7 @@ static cJSON_bool print_number(const cJSON * const item, printbuffer * const out
         length = sprintf((char*)number_buffer, "%1.15g", d);
 
         /* Check whether the original double can be recovered */
-        if ((sscanf((char*)number_buffer, "%lg", &test) != 1) || ((double)test != d))
+        if ((sscanf((char*)number_buffer, "%lg", &test) != 1) || !compare_double((double)test, d))
         {
             /* If not, print with 17 decimal places of precision */
             length = sprintf((char*)number_buffer, "%1.17g", d);
@@ -2876,7 +2882,7 @@ CJSON_PUBLIC(cJSON_bool) cJSON_Compare(const cJSON * const a, const cJSON * cons
             return true;
 
         case cJSON_Number:
-            if (a->valuedouble == b->valuedouble)
+            if (compare_double(a->valuedouble, b->valuedouble))
             {
                 return true;
             }

cJSON.h

@@ -137,6 +137,11 @@ typedef int cJSON_bool;
 #define CJSON_NESTING_LIMIT 1000
 #endif
 
+/* Precision of double variables comparison */
+#ifndef CJSON_DOUBLE_PRECIION
+#define CJSON_DOUBLE_PRECIION .00001
+#endif
+
 /* returns the version of cJSON as a string */
 CJSON_PUBLIC(const char*) cJSON_Version(void);
 

cJSON_Utils.c

@@ -39,6 +39,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <limits.h>
+#include <math.h>
 
 #if defined(_MSC_VER)
 #pragma warning (pop)
@@ -105,6 +106,13 @@ static int compare_strings(const unsigned char *string1, const unsigned char *st
     return tolower(*string1) - tolower(*string2);
 }
 
+/* securely comparison of floating-point variables */
+static cJSON_bool compare_double(double a, double b)
+{
+    return (fabs(a - b) <= a * CJSON_DOUBLE_PRECIION);
+}
+
+
 /* Compare the next path element of two JSON pointers, two NULL pointers are considered unequal: */
 static cJSON_bool compare_pointers(const unsigned char *name, const unsigned char *pointer, const cJSON_bool case_sensitive)
 {
@@ -596,7 +604,7 @@ static cJSON_bool compare_json(cJSON *a, cJSON *b, const cJSON_bool case_sensiti
     {
         case cJSON_Number:
             /* numeric mismatch. */
-            if ((a->valueint != b->valueint) || (a->valuedouble != b->valuedouble))
+            if ((a->valueint != b->valueint) || (!compare_double(a->valuedouble, b->valuedouble)))
             {
                 return false;
             }
@@ -1136,7 +1144,7 @@ static void create_patches(cJSON * const patches, const unsigned char * const pa
     switch (from->type & 0xFF)
     {
         case cJSON_Number:
-            if ((from->valueint != to->valueint) || (from->valuedouble != to->valuedouble))
+            if ((from->valueint != to->valueint) || (compare_double(from->valuedouble, to->valuedouble)))
             {
                 compose_patch(patches, (const unsigned char*)"replace", path, NULL, to);
             }