Library configuration: Enable configuring the direction of arguments. (#1717)

This enhances the library configuration so the direction of function
arguments can be specified (in, out, inout).
isVariableChangedByFunctionCall() uses this information now to avoid
guessing.

cfg/cppcheck-cfg.rng

@@ -163,6 +163,11 @@
                   <text/>
                 </attribute>
               </optional>
+              <optional>
+                <attribute name="direction">
+                  <ref name="ARG-DIRECTION"/>
+                </attribute>
+              </optional>
 
               <interleave>
                 <optional>
@@ -425,6 +430,14 @@
       <param name="maxInclusive">20</param>
     </data>
   </define>
+  
+  <define name="ARG-DIRECTION">
+    <choice>
+      <value>in</value>
+      <value>out</value>
+      <value>inout</value>
+    </choice>
+  </define>
 
   <define name="DATA-BOOL">
     <choice>

cfg/std.cfg

@@ -52,7 +52,7 @@
     <returnValue type="int">arg1&gt;0?arg1:-arg1</returnValue>
     <noreturn>false</noreturn>
     <leak-ignore/>
-    <arg nr="1">
+    <arg nr="1" direction="in">
       <not-uninit/>
       <not-bool/>
     </arg>
@@ -448,10 +448,10 @@
     <returnValue type="size_t"/>
     <noreturn>false</noreturn>
     <leak-ignore/>
-    <arg nr="1">
+    <arg nr="1" direction="out">
       <not-null/>
     </arg>
-    <arg nr="2">
+    <arg nr="2" direction="in">
       <not-uninit/>
     </arg>
     <arg nr="3">
@@ -4115,7 +4115,7 @@ The obsolete function 'gets' is called. With 'gets' you'll get a buffer overrun
     <noreturn>false</noreturn>
     <leak-ignore/>
     <formatstr/>
-    <arg nr="1">
+    <arg nr="1" direction="in">
       <formatstr/>
       <not-uninit/>
     </arg>
@@ -4505,12 +4505,12 @@ The obsolete function 'gets' is called. With 'gets' you'll get a buffer overrun
     <returnValue type="char *"/>
     <noreturn>false</noreturn>
     <leak-ignore/>
-    <arg nr="1">
+    <arg nr="1" direction="inout">
       <not-null/>
       <not-uninit/>
       <strz/>
     </arg>
-    <arg nr="2">
+    <arg nr="2" direction="in">
       <not-null/>
       <not-uninit/>
       <strz/>
@@ -5734,12 +5734,12 @@ The obsolete function 'gets' is called. With 'gets' you'll get a buffer overrun
     <returnValue type="int"/>
     <noreturn>false</noreturn>
     <leak-ignore/>
-    <arg nr="1">
+    <arg nr="1" direction="out">
       <not-uninit/>
       <minsize type="strlen" arg="2"/>
     </arg>
     <formatstr/>
-    <arg nr="2">
+    <arg nr="2" direction="in">
       <formatstr/>
       <not-null/>
       <not-uninit/>

lib/astutils.cpp

@@ -880,6 +880,16 @@ bool isVariableChangedByFunctionCall(const Token *tok, const Settings *settings,
     }
 
     if (!tok->function()) {
+        // Check if direction (in, out, inout) is specified in the library configuration and use that
+        if (!addressOf && settings) {
+            const Library::ArgumentChecks::Direction argDirection = settings->library.getArgDirection(tok, 1 + argnr);
+            if (argDirection == Library::ArgumentChecks::Direction::DIR_IN)
+                return false;
+            else if (argDirection == Library::ArgumentChecks::Direction::DIR_OUT ||
+                     argDirection == Library::ArgumentChecks::Direction::DIR_INOUT)
+                return true;
+        }
+
         // if the library says 0 is invalid
         // => it is assumed that parameter is an in parameter (TODO: this is a bad heuristic)
         if (!addressOf && settings && settings->library.isnullargbad(tok, 1+argnr))

lib/library.cpp

@@ -581,6 +581,17 @@ Library::Error Library::loadFunction(const tinyxml2::XMLElement * const node, co
             ArgumentChecks &ac = func.argumentChecks[nr];
             ac.optional  = functionnode->Attribute("default") != nullptr;
             ac.variadic = bVariadicArg;
+            const char * const argDirection = functionnode->Attribute("direction");
+            if (argDirection) {
+                const size_t argDirLen = strlen(argDirection);
+                if (!strncmp(argDirection, "in", argDirLen)) {
+                    ac.direction = ArgumentChecks::Direction::DIR_IN;
+                } else if (!strncmp(argDirection, "out", argDirLen)) {
+                    ac.direction = ArgumentChecks::Direction::DIR_OUT;
+                } else if (!strncmp(argDirection, "inout", argDirLen)) {
+                    ac.direction = ArgumentChecks::Direction::DIR_INOUT;
+                }
+            }
             for (const tinyxml2::XMLElement *argnode = functionnode->FirstChildElement(); argnode; argnode = argnode->NextSiblingElement()) {
                 const std::string argnodename = argnode->Name();
                 if (argnodename == "not-bool")

lib/library.h

@@ -227,7 +227,8 @@ public:
             strz(false),
             optional(false),
             variadic(false),
-            iteratorInfo() {
+            iteratorInfo(),
+            direction(DIR_UNKNOWN) {
         }
 
         bool         notbool;
@@ -259,6 +260,9 @@ public:
             int arg2;
         };
         std::vector<MinSize> minsizes;
+
+        enum Direction { DIR_IN, DIR_OUT, DIR_INOUT, DIR_UNKNOWN };
+        Direction direction;
     };
 
 
@@ -320,6 +324,11 @@ public:
         return arg ? &arg->minsizes : nullptr;
     }
 
+    ArgumentChecks::Direction getArgDirection(const Token *ftok, int argnr) const {
+        const ArgumentChecks *arg = getarg(ftok, argnr);
+        return arg ? arg->direction : ArgumentChecks::Direction::DIR_UNKNOWN;
+    }
+
     bool markupFile(const std::string &path) const;
 
     bool processMarkupAfterCode(const std::string &path) const;