diff --git a/lib/mathlib.cpp b/lib/mathlib.cpp
index e332d2b8d..a7a6bd473 100644
--- a/lib/mathlib.cpp
+++ b/lib/mathlib.cpp
@@ -546,7 +546,7 @@ bool MathLib::isDecimalFloat(const std::string &str)
     if (str.empty())
         return false;
     enum class State {
-        START, BASE_DIGITS1, LEADING_DECIMAL, TRAILING_DECIMAL, BASE_DIGITS2, E, MANTISSA_PLUSMINUS, MANTISSA_DIGITS, SUFFIX_F, SUFFIX_L
+        START, BASE_DIGITS1, LEADING_DECIMAL, TRAILING_DECIMAL, BASE_DIGITS2, E, MANTISSA_PLUSMINUS, MANTISSA_DIGITS, SUFFIX_F, SUFFIX_L, SUFFIX_LITERAL_LEADER, SUFFIX_LITERAL
     } state = State::START;
     std::string::const_iterator it = str.cbegin();
     if ('+' == *it || '-' == *it)
@@ -582,6 +582,8 @@ bool MathLib::isDecimalFloat(const std::string &str)
                 state = State::SUFFIX_F;
             else if (*it=='l' || *it=='L')
                 state = State::SUFFIX_L;
+            else if (*it == '_')
+                state = State::SUFFIX_LITERAL_LEADER;
             else if (std::isdigit(static_cast<unsigned char>(*it)))
                 state = State::BASE_DIGITS2;
             else
@@ -594,6 +596,8 @@ bool MathLib::isDecimalFloat(const std::string &str)
                 state = State::SUFFIX_F;
             else if (*it=='l' || *it=='L')
                 state = State::SUFFIX_L;
+            else if (*it == '_')
+                state = State::SUFFIX_LITERAL_LEADER;
             else if (!std::isdigit(static_cast<unsigned char>(*it)))
                 return false;
             break;
@@ -619,13 +623,18 @@ bool MathLib::isDecimalFloat(const std::string &str)
             else if (!std::isdigit(static_cast<unsigned char>(*it)))
                 return false;
             break;
+        // Ensure at least one post _ char for user defined literals
+        case State::SUFFIX_LITERAL:
+        case State::SUFFIX_LITERAL_LEADER:
+            state = State::SUFFIX_LITERAL;
+            break;
         case State::SUFFIX_F:
             return false;
         case State::SUFFIX_L:
             return false;
         }
     }
-    return (state==State::BASE_DIGITS2 || state==State::MANTISSA_DIGITS || state==State::TRAILING_DECIMAL || state==State::SUFFIX_F || state==State::SUFFIX_L);
+    return (state==State::BASE_DIGITS2 || state==State::MANTISSA_DIGITS || state==State::TRAILING_DECIMAL || state==State::SUFFIX_F || state==State::SUFFIX_L || (state==State::SUFFIX_LITERAL));
 }
 
 bool MathLib::isNegative(const std::string &str)
@@ -644,7 +653,7 @@ bool MathLib::isPositive(const std::string &str)
 
 static bool isValidIntegerSuffixIt(std::string::const_iterator it, std::string::const_iterator end, bool supportMicrosoftExtensions=true)
 {
-    enum class Status { START, SUFFIX_U, SUFFIX_UL, SUFFIX_ULL, SUFFIX_L, SUFFIX_LU, SUFFIX_LL, SUFFIX_LLU, SUFFIX_I, SUFFIX_I6, SUFFIX_I64, SUFFIX_UI, SUFFIX_UI6, SUFFIX_UI64 } state = Status::START;
+    enum class Status { START, SUFFIX_U, SUFFIX_UL, SUFFIX_ULL, SUFFIX_UZ, SUFFIX_L, SUFFIX_LU, SUFFIX_LL, SUFFIX_LLU, SUFFIX_I, SUFFIX_I6, SUFFIX_I64, SUFFIX_UI, SUFFIX_UI6, SUFFIX_UI64, SUFFIX_Z, SUFFIX_LITERAL_LEADER, SUFFIX_LITERAL } state = Status::START;
     for (; it != end; ++it) {
         switch (state) {
         case Status::START:
@@ -652,14 +661,20 @@ static bool isValidIntegerSuffixIt(std::string::const_iterator it, std::string::
                 state = Status::SUFFIX_U;
             else if (*it == 'l' || *it == 'L')
                 state = Status::SUFFIX_L;
+            else if (*it == 'z' || *it == 'Z')
+                state = Status::SUFFIX_Z;
             else if (supportMicrosoftExtensions && (*it == 'i' || *it == 'I'))
                 state = Status::SUFFIX_I;
+            else if (*it == '_')
+                state = Status::SUFFIX_LITERAL_LEADER;
             else
                 return false;
             break;
         case Status::SUFFIX_U:
             if (*it == 'l' || *it == 'L')
                 state = Status::SUFFIX_UL; // UL
+            else if (*it == 'z' || *it == 'Z')
+                state = Status::SUFFIX_UZ; // UZ
             else if (supportMicrosoftExtensions && (*it == 'i' || *it == 'I'))
                 state = Status::SUFFIX_UI;
             else
@@ -711,19 +726,33 @@ static bool isValidIntegerSuffixIt(std::string::const_iterator it, std::string::
             else
                 return false;
             break;
+        case Status::SUFFIX_Z:
+            if (*it == 'u' || *it == 'U')
+                state = Status::SUFFIX_UZ;
+            else
+                return false;
+            break;
+        // Ensure at least one post _ char for user defined literals
+        case Status::SUFFIX_LITERAL:
+        case Status::SUFFIX_LITERAL_LEADER:
+            state = Status::SUFFIX_LITERAL;
+            break;
         default:
             return false;
         }
     }
     return ((state == Status::SUFFIX_U) ||
             (state == Status::SUFFIX_L) ||
+            (state == Status::SUFFIX_Z) ||
             (state == Status::SUFFIX_UL) ||
+            (state == Status::SUFFIX_UZ) ||
             (state == Status::SUFFIX_LU) ||
             (state == Status::SUFFIX_LL) ||
             (state == Status::SUFFIX_ULL) ||
             (state == Status::SUFFIX_LLU) ||
             (state == Status::SUFFIX_I64) ||
-            (state == Status::SUFFIX_UI64));
+            (state == Status::SUFFIX_UI64) ||
+            (state == Status::SUFFIX_LITERAL));
 }
 
 // cppcheck-suppress unusedFunction
diff --git a/test/testmathlib.cpp b/test/testmathlib.cpp
index d02598f04..e49d08afa 100644
--- a/test/testmathlib.cpp
+++ b/test/testmathlib.cpp
@@ -960,6 +960,14 @@ private:
         ASSERT_EQUALS(true, MathLib::isIntHex("-0x0ULL"));
         ASSERT_EQUALS(true, MathLib::isIntHex("+0x0LLU"));
         ASSERT_EQUALS(true, MathLib::isIntHex("-0x0LLU"));
+        ASSERT_EQUALS(true, MathLib::isIntHex("+0x0Z"));
+        ASSERT_EQUALS(true, MathLib::isIntHex("-0x0Z"));
+        ASSERT_EQUALS(true, MathLib::isIntHex("+0x0ZU"));
+        ASSERT_EQUALS(true, MathLib::isIntHex("-0x0ZU"));
+        ASSERT_EQUALS(true, MathLib::isIntHex("+0x0UZ"));
+        ASSERT_EQUALS(true, MathLib::isIntHex("-0x0UZ"));
+        ASSERT_EQUALS(true, MathLib::isIntHex("+0x0Uz"));
+        ASSERT_EQUALS(true, MathLib::isIntHex("-0x0Uz"));
 
         // negative testing
         ASSERT_EQUALS(false, MathLib::isIntHex("+0x"));
@@ -972,10 +980,6 @@ private:
         ASSERT_EQUALS(false, MathLib::isIntHex("  "));
         ASSERT_EQUALS(false, MathLib::isIntHex(" "));
         ASSERT_EQUALS(false, MathLib::isIntHex("0"));
-        ASSERT_EQUALS(false, MathLib::isIntHex("+0x0Z"));
-        ASSERT_EQUALS(false, MathLib::isIntHex("-0x0Z"));
-        ASSERT_EQUALS(false, MathLib::isIntHex("+0x0Uz"));
-        ASSERT_EQUALS(false, MathLib::isIntHex("-0x0Uz"));
         ASSERT_EQUALS(false, MathLib::isIntHex("+0x0Lz"));
         ASSERT_EQUALS(false, MathLib::isIntHex("-0x0Lz"));
         ASSERT_EQUALS(false, MathLib::isIntHex("+0x0LUz"));
@@ -1018,12 +1022,19 @@ private:
         ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("u"));
         ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("ul"));
         ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("ull"));
+        ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("uz"));
         ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("l"));
         ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("lu"));
         ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("ll"));
         ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("llu"));
         ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("llU"));
         ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("LLU"));
+        ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("z"));
+        ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("Z"));
+        ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("zu"));
+        ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("UZ"));
+        ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("ZU"));
+
         // Microsoft extensions:
         ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("i64"));
         ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("I64"));
@@ -1033,6 +1044,10 @@ private:
         ASSERT_EQUALS(false, MathLib::isValidIntegerSuffix("I64", false));
         ASSERT_EQUALS(false, MathLib::isValidIntegerSuffix("ui64", false));
         ASSERT_EQUALS(false, MathLib::isValidIntegerSuffix("UI64", false));
+
+        // User defined suffix literals
+        ASSERT_EQUALS(false, MathLib::isValidIntegerSuffix("_"));
+        ASSERT_EQUALS(true, MathLib::isValidIntegerSuffix("_MyUserDefinedLiteral"));
     }
 
     void ispositive() const {
@@ -1057,6 +1072,13 @@ private:
         ASSERT_EQUALS(true,  MathLib::isFloat("0.f"));
         ASSERT_EQUALS(true,  MathLib::isFloat("0.f"));
         ASSERT_EQUALS(true,  MathLib::isFloat("0xA.Fp-10"));
+
+        // User defined suffix literals
+        ASSERT_EQUALS(false, MathLib::isFloat("0_"));
+        ASSERT_EQUALS(false, MathLib::isFloat("0._"));
+        ASSERT_EQUALS(false, MathLib::isFloat("0.1_"));
+        ASSERT_EQUALS(true, MathLib::isFloat("0.0_MyUserDefinedLiteral"));
+        ASSERT_EQUALS(true, MathLib::isFloat("0._MyUserDefinedLiteral"));
     }
 
     void isDecimalFloat() const {
@@ -1164,6 +1186,13 @@ private:
         ASSERT_EQUALS(true, MathLib::isDecimalFloat("1.0E+1"));
         ASSERT_EQUALS(true, MathLib::isDecimalFloat("1.0E-1"));
         ASSERT_EQUALS(true, MathLib::isDecimalFloat("-1.0E+1"));
+
+        // User defined suffix literals
+        ASSERT_EQUALS(false, MathLib::isDecimalFloat("0_"));
+        ASSERT_EQUALS(false, MathLib::isDecimalFloat(".1_"));
+        ASSERT_EQUALS(false, MathLib::isDecimalFloat("0.1_"));
+        ASSERT_EQUALS(true, MathLib::isDecimalFloat("0.0_MyUserDefinedLiteral"));
+        ASSERT_EQUALS(true, MathLib::isDecimalFloat(".1_MyUserDefinedLiteral"));
     }
 
     void naninf() const {
@@ -1198,6 +1227,14 @@ private:
         ASSERT_EQUALS(false, MathLib::isDec("+x"));
         ASSERT_EQUALS(false, MathLib::isDec("x"));
         ASSERT_EQUALS(false, MathLib::isDec(""));
+
+        // User defined suffix literals
+        ASSERT_EQUALS(false, MathLib::isDec("0_"));
+        ASSERT_EQUALS(false, MathLib::isDec("+0_"));
+        ASSERT_EQUALS(false, MathLib::isDec("-1_"));
+        ASSERT_EQUALS(true, MathLib::isDec("0_MyUserDefinedLiteral"));
+        ASSERT_EQUALS(true, MathLib::isDec("+1_MyUserDefinedLiteral"));
+        ASSERT_EQUALS(true, MathLib::isDec("-1_MyUserDefinedLiteral"));
     }
 
     void isNullValue() const {