From c297ed8204a1d6472b9eff90b6aa1029aea932d8 Mon Sep 17 00:00:00 2001
From: Ken-Patrick Lehrmann <kp.lehrmann+github@gmail.com>
Date: Wed, 17 Jun 2020 19:01:32 +0200
Subject: [PATCH] Better handle noreturn or throwing functions in valueflow

Teaching cppcheck about `BOOST_THROW_EXCEPTION` and
`boost::throw_exception`, and using noreturn information from libraries
in value flow.

This fixes false positive nullPointerRedundantCheck with the following
code:
```
void throwexception(int * buf)
{
    if (!buf)
        boost::throw_exception(std::bad_alloc());
    *buf = 0;
}
```
---
 cfg/boost.cfg      |  7 +++++++
 lib/astutils.cpp   | 16 ++++++++++------
 test/cfg/boost.cpp | 14 ++++++++++++++
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/cfg/boost.cfg b/cfg/boost.cfg
index 87f7493df..40ec3a4a3 100644
--- a/cfg/boost.cfg
+++ b/cfg/boost.cfg
@@ -17,6 +17,7 @@
   <define name="BOOST_FORCEINLINE" value="inline"/>
   <define name="BOOST_NOINLINE" value=""/>
   <define name="BOOST_NORETURN" value="[[noreturn]]"/>
+  <define name="BOOST_THROW_EXCEPTION(X)" value="boost::throw_exception(X)"/>
   <define name="BOOST_LIKELY(X)" value="(X)"/>
   <define name="BOOST_UNLIKELY(X)" value="(X)"/>
   <define name="BOOST_FIXTURE_TEST_SUITE(...)" value=""/>
@@ -968,4 +969,10 @@
       <not-bool/>
     </arg>
   </function>
+  <function name="boost::throw_exception">                                                             
+    <noreturn>true</noreturn>                                                                          
+    <arg nr="1" direction="in">                                                                        
+      <not-uninit/>                                                                                    
+    </arg>                                                                                             
+  </function>            
 </def>
diff --git a/lib/astutils.cpp b/lib/astutils.cpp
index bff663e01..c0ab6c08f 100644
--- a/lib/astutils.cpp
+++ b/lib/astutils.cpp
@@ -1066,16 +1066,20 @@ bool isUniqueExpression(const Token* tok)
     return isUniqueExpression(tok->astOperand2());
 }
 
-static bool isEscaped(const Token* tok, bool functionsScope)
+static bool isEscaped(const Token* tok, bool functionsScope, const Library* library)
 {
+    if (library && library->isnoreturn(tok))
+        return true;
     if (functionsScope)
         return Token::simpleMatch(tok, "throw");
     else
         return Token::Match(tok, "return|throw");
 }
 
-static bool isEscapedOrJump(const Token* tok, bool functionsScope)
+static bool isEscapedOrJump(const Token* tok, bool functionsScope, const Library* library)
 {
+    if (library && library->isnoreturn(tok))
+        return true;
     if (functionsScope)
         return Token::simpleMatch(tok, "throw");
     else
@@ -1148,7 +1152,7 @@ bool isReturnScope(const Token* const endToken, const Library* library, const To
             !Token::findsimplematch(prev->link(), "break", prev)) {
             return true;
         }
-        if (isEscaped(prev->link()->astTop(), functionScope))
+        if (isEscaped(prev->link()->astTop(), functionScope, library))
             return true;
         if (Token::Match(prev->link()->previous(), "[;{}] {"))
             return isReturnScope(prev, library, unknownFunc, functionScope);
@@ -1162,13 +1166,13 @@ bool isReturnScope(const Token* const endToken, const Library* library, const To
             return false;
         }
         if (Token::simpleMatch(prev->previous(), ") ;") && prev->previous()->link() &&
-            isEscaped(prev->previous()->link()->astTop(), functionScope))
+            isEscaped(prev->previous()->link()->astTop(), functionScope, library))
             return true;
-        if (isEscaped(prev->previous()->astTop(), functionScope))
+        if (isEscaped(prev->previous()->astTop(), functionScope, library))
             return true;
         // return/goto statement
         prev = prev->previous();
-        while (prev && !Token::Match(prev, ";|{|}") && !isEscapedOrJump(prev, functionScope))
+        while (prev && !Token::Match(prev, ";|{|}") && !isEscapedOrJump(prev, functionScope, library))
             prev = prev->previous();
         return prev && prev->isName();
     }
diff --git a/test/cfg/boost.cpp b/test/cfg/boost.cpp
index a83f7e604..0ef74ac71 100644
--- a/test/cfg/boost.cpp
+++ b/test/cfg/boost.cpp
@@ -67,3 +67,17 @@ void uninitvar()
     // cppcheck-suppress uninitvar
     (void)boost::math::round(intUninit2);
 }
+
+void throwexception(int * buf)
+{
+    if (!buf)
+        boost::throw_exception(std::bad_alloc());
+    *buf = 0;
+}
+
+void throwexception2(int * buf)
+{
+    if (!buf)
+        BOOST_THROW_EXCEPTION(std::bad_alloc());
+    *buf = 0;
+}