diff --git a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
--- a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
@@ -105,6 +105,11 @@
   /// Get a string representation of an argument index.
   /// E.g.: (1) -> '1st arg', (2) - > '2nd arg'
   static void printArgDesc(ArgNo, llvm::raw_ostream &Out);
+  /// Print value X of the argument in form " (that is X)",
+  /// if the value is a fixed known value, otherwise print nothing.
+  /// This is used as simple explanation of values if possible.
+  static void printArgValueInfo(ArgNo ArgN, ProgramStateRef State,
+                                const CallEvent &Call, llvm::raw_ostream &Out);
   /// Append textual description of a numeric range [RMin,RMax] to
   /// \p Out.
   static void appendInsideRangeDesc(llvm::APSInt RMin, llvm::APSInt RMax,
@@ -435,6 +440,10 @@
                   ProgramStateRef State, const Summary &Summary,
                   llvm::raw_ostream &Out) const override;
 
+    bool describeArgumentValue(const CallEvent &Call, ProgramStateRef State,
+                               const Summary &Summary,
+                               llvm::raw_ostream &Out) const override;
+
     std::vector<ArgNo> getArgsToTrack() const override {
       std::vector<ArgNo> Result{ArgN};
       if (SizeArgN)
@@ -870,6 +879,16 @@
   Out << " argument";
 }
 
+void StdLibraryFunctionsChecker::printArgValueInfo(ArgNo ArgN,
+                                                   ProgramStateRef State,
+                                                   const CallEvent &Call,
+                                                   llvm::raw_ostream &Out) {
+  if (const llvm::APSInt *Val =
+          State->getStateManager().getSValBuilder().getKnownValue(
+              State, getArgSVal(Call, ArgN)))
+    Out << " (that is " << *Val << ")";
+}
+
 void StdLibraryFunctionsChecker::appendInsideRangeDesc(llvm::APSInt RMin,
                                                        llvm::APSInt RMax,
                                                        QualType ArgT,
@@ -1179,13 +1198,29 @@
   } else if (SizeArgN) {
     Out << "the value of the ";
     printArgDesc(*SizeArgN, Out);
+    printArgValueInfo(*SizeArgN, State, Call, Out);
     if (SizeMultiplierArgN) {
       Out << " times the ";
       printArgDesc(*SizeMultiplierArgN, Out);
+      printArgValueInfo(*SizeMultiplierArgN, State, Call, Out);
     }
   }
 }
 
+bool StdLibraryFunctionsChecker::BufferSizeConstraint::describeArgumentValue(
+    const CallEvent &Call, ProgramStateRef State, const Summary &Summary,
+    llvm::raw_ostream &Out) const {
+  SVal BufV = getArgSVal(Call, getArgNo());
+  SVal BufDynSize = getDynamicExtentWithOffset(State, BufV);
+  if (const llvm::APSInt *Val =
+          State->getStateManager().getSValBuilder().getKnownValue(State,
+                                                                  BufDynSize)) {
+    Out << "is a buffer with size " << *Val;
+    return true;
+  }
+  return false;
+}
+
 void StdLibraryFunctionsChecker::checkPreCall(const CallEvent &Call,
                                               CheckerContext &C) const {
   std::optional<Summary> FoundSummary = findFunctionSummary(Call, C);
diff --git a/clang/test/Analysis/std-c-library-functions-arg-constraints-notes.cpp b/clang/test/Analysis/std-c-library-functions-arg-constraints-notes.cpp
--- a/clang/test/Analysis/std-c-library-functions-arg-constraints-notes.cpp
+++ b/clang/test/Analysis/std-c-library-functions-arg-constraints-notes.cpp
@@ -28,19 +28,19 @@
   case 1: {
     char buf[9];
     __buf_size_arg_constraint_concrete(buf); // \
-    // expected-warning{{The 1st argument to '__buf_size_arg_constraint_concrete' is out of the accepted range; It should be a buffer with size equal to or greater than 10 [}}
+    // expected-warning{{The 1st argument to '__buf_size_arg_constraint_concrete' is a buffer with size 9 but should be a buffer with size equal to or greater than 10 [}}
     break;
   }
   case 2: {
     char buf[3];
     __buf_size_arg_constraint(buf, 4); // \
-    // expected-warning{{The 1st argument to '__buf_size_arg_constraint' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument}}
+    // expected-warning{{The 1st argument to '__buf_size_arg_constraint' is a buffer with size 3 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4) [}}
     break;
   }
   case 3: {
     char buf[3];
     __buf_size_arg_constraint_mul(buf, 4, 2); // \
-    // expected-warning{{The 1st argument to '__buf_size_arg_constraint_mul' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument times the 3rd argument}}
+    // expected-warning{{The 1st argument to '__buf_size_arg_constraint_mul' is a buffer with size 3 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4) times the 3rd argument (that is 2) [}}
     break;
   }
   }
diff --git a/clang/test/Analysis/std-c-library-functions-arg-constraints-tracking-notes.c b/clang/test/Analysis/std-c-library-functions-arg-constraints-tracking-notes.c
--- a/clang/test/Analysis/std-c-library-functions-arg-constraints-tracking-notes.c
+++ b/clang/test/Analysis/std-c-library-functions-arg-constraints-tracking-notes.c
@@ -16,8 +16,8 @@
   char buf[3];                       // bugpath-note{{'buf' initialized here}}
   int s = 4;                         // bugpath-note{{'s' initialized to 4}}
   __buf_size_arg_constraint(buf, s); // \
-  // bugpath-warning{{The 1st argument to '__buf_size_arg_constraint' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument}} \
-  // bugpath-note{{The 1st argument to '__buf_size_arg_constraint' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument}}
+  // bugpath-warning{{The 1st argument to '__buf_size_arg_constraint' is a buffer with size 3 but should be a buffer with size equal to or greater than the value of the 2nd argument}} \
+  // bugpath-note{{The 1st argument to '__buf_size_arg_constraint' is a buffer with size 3 but should be a buffer with size equal to or greater than the value of the 2nd argument}}
 }
 
 int __buf_size_arg_constraint_mul(const void *, size_t, size_t);
@@ -26,6 +26,6 @@
   int s1 = 4;                                 // bugpath-note{{'s1' initialized to 4}}
   int s2 = sizeof(short);                     // bugpath-note{{'s2' initialized to}}
   __buf_size_arg_constraint_mul(buf, s1, s2); // \
-  // bugpath-warning{{The 1st argument to '__buf_size_arg_constraint_mul' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument times the 3rd argument}} \
-  // bugpath-note{{The 1st argument to '__buf_size_arg_constraint_mul' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument times the 3rd argument}}
+  // bugpath-warning{{The 1st argument to '__buf_size_arg_constraint_mul' is a buffer with size 6 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4) times the 3rd argument (that is 2)}} \
+  // bugpath-note{{The 1st argument to '__buf_size_arg_constraint_mul' is a buffer with size 6 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4) times the 3rd argument (that is 2)}}
 }
diff --git a/clang/test/Analysis/std-c-library-functions-arg-constraints.c b/clang/test/Analysis/std-c-library-functions-arg-constraints.c
--- a/clang/test/Analysis/std-c-library-functions-arg-constraints.c
+++ b/clang/test/Analysis/std-c-library-functions-arg-constraints.c
@@ -210,9 +210,9 @@
   // The 3rd parameter should be the number of elements to read, not
   // the size in bytes.
   fread(wbuf, size, nitems, file); // \
-  // report-warning{{The 1st argument to 'fread' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument times the 3rd argument}} \
-  // bugpath-warning{{The 1st argument to 'fread' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument times the 3rd argument}} \
-  // bugpath-note{{The 1st argument to 'fread' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument times the 3rd argument}}
+  // report-warning{{The 1st argument to 'fread' is a buffer with size 4096 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4) times the 3rd argument (that is 4096)}} \
+  // bugpath-warning{{The 1st argument to 'fread' is a buffer with size 4096 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4) times the 3rd argument (that is 4096)}} \
+  // bugpath-note{{The 1st argument to 'fread' is a buffer with size 4096 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4) times the 3rd argument (that is 4096)}}
 }
 
 int __two_constrained_args(int, int);
@@ -254,9 +254,9 @@
 void test_buf_size_concrete(void) {
   char buf[3];                       // bugpath-note{{'buf' initialized here}}
   __buf_size_arg_constraint(buf, 4); // \
-  // report-warning{{The 1st argument to '__buf_size_arg_constraint' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument}} \
-  // bugpath-warning{{The 1st argument to '__buf_size_arg_constraint' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument}} \
-  // bugpath-note{{The 1st argument to '__buf_size_arg_constraint' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument}}
+  // report-warning{{The 1st argument to '__buf_size_arg_constraint' is a buffer with size 3 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4)}} \
+  // bugpath-warning{{The 1st argument to '__buf_size_arg_constraint' is a buffer with size 3 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4)}} \
+  // bugpath-note{{The 1st argument to '__buf_size_arg_constraint' is a buffer with size 3 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4)}}
 }
 void test_buf_size_symbolic(int s) {
   char buf[3];
@@ -281,9 +281,9 @@
 void test_buf_size_concrete_with_multiplication(void) {
   short buf[3];                                         // bugpath-note{{'buf' initialized here}}
   __buf_size_arg_constraint_mul(buf, 4, sizeof(short)); // \
-  // report-warning{{The 1st argument to '__buf_size_arg_constraint_mul' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument times the 3rd argument}} \
-  // bugpath-warning{{The 1st argument to '__buf_size_arg_constraint_mul' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument times the 3rd argument}} \
-  // bugpath-note{{The 1st argument to '__buf_size_arg_constraint_mul' is out of the accepted range; It should be a buffer with size equal to or greater than the value of the 2nd argument times the 3rd argument}}
+  // report-warning{{The 1st argument to '__buf_size_arg_constraint_mul' is a buffer with size 6 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4) times the 3rd argument (that is 2)}} \
+  // bugpath-warning{{The 1st argument to '__buf_size_arg_constraint_mul' is a buffer with size 6 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4) times the 3rd argument (that is 2)}} \
+  // bugpath-note{{The 1st argument to '__buf_size_arg_constraint_mul' is a buffer with size 6 but should be a buffer with size equal to or greater than the value of the 2nd argument (that is 4) times the 3rd argument (that is 2)}}
 }
 void test_buf_size_symbolic_with_multiplication(size_t s) {
   short buf[3];
@@ -307,9 +307,9 @@
 void test_min_buf_size(void) {
   char buf[9];// bugpath-note{{'buf' initialized here}}
   __buf_size_arg_constraint_concrete(buf); // \
-  // report-warning{{The 1st argument to '__buf_size_arg_constraint_concrete' is out of the accepted range; It should be a buffer with size equal to or greater than 10}} \
-  // bugpath-warning{{The 1st argument to '__buf_size_arg_constraint_concrete' is out of the accepted range; It should be a buffer with size equal to or greater than 10}} \
-  // bugpath-note{{The 1st argument to '__buf_size_arg_constraint_concrete' is out of the accepted range; It should be a buffer with size equal to or greater than 10}}
+  // report-warning{{The 1st argument to '__buf_size_arg_constraint_concrete' is a buffer with size 9 but should be a buffer with size equal to or greater than 10}} \
+  // bugpath-warning{{The 1st argument to '__buf_size_arg_constraint_concrete' is a buffer with size 9 but should be a buffer with size equal to or greater than 10}} \
+  // bugpath-note{{The 1st argument to '__buf_size_arg_constraint_concrete' is a buffer with size 9 but should be a buffer with size equal to or greater than 10}}
 }
 
 void test_file_fd_at_functions() {