Don't suggest the developer use 'arc4random' instead of 'rand' when that function is not available. Fixes PR 6012.

llvm-svn: 93508

clang/lib/Analysis/CheckSecuritySyntaxOnly.cpp

@@ -11,6 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/Basic/TargetInfo.h"
 #include "clang/Analysis/PathSensitive/BugReporter.h"
 #include "clang/Analysis/LocalCheckers.h"
 #include "clang/AST/StmtVisitor.h"
@@ -18,6 +19,12 @@
 
 using namespace clang;
 
+static bool isArc4RandomAvailable(const ASTContext &Ctx) {
+  const llvm::Triple &T = Ctx.Target.getTriple();
+  return T.getVendor() == llvm::Triple::Apple ||
+         T.getOS() == llvm::Triple::FreeBSD;
+}
+
 namespace {
 class WalkAST : public StmtVisitor<WalkAST> {
   BugReporter &BR;
@@ -30,10 +37,13 @@ class WalkAST : public StmtVisitor<WalkAST> {
   enum { num_setids = 6 };
   IdentifierInfo *II_setid[num_setids];
   
+  const bool CheckRand;
+
 public:
   WalkAST(BugReporter &br) : BR(br),
 			     II_gets(0), II_getpw(0), II_mktemp(0),
-			     II_rand(), II_random(0), II_setid() {}
+			     II_rand(), II_random(0), II_setid(),
+                 CheckRand(isArc4RandomAvailable(BR.getContext())) {}
 
   // Statement visitor methods.
   void VisitCallExpr(CallExpr *CE);
@@ -83,9 +93,11 @@ void WalkAST::VisitCallExpr(CallExpr *CE) {
     CheckCall_gets(CE, FD);
     CheckCall_getpw(CE, FD);
     CheckCall_mktemp(CE, FD);
+    if (CheckRand) {
       CheckCall_rand(CE, FD);
       CheckCall_random(CE, FD);
     }
+  }
 
   // Recurse and check children.
   VisitChildren(CE);

clang/test/Analysis/security-syntax-checks-no-emit.c

@@ -0,0 +1,33 @@
+// RUN: %clang_cc1 -triple i686-pc-linux-gnu -analyze -warn-security-syntactic %s -verify
+
+// This file complements 'security-syntax-checks.m', but tests that we omit
+// specific checks on platforms where they don't make sense.
+
+// Omit the 'rand' check since 'arc4random' is not available on Linux.
+int      rand(void);
+double   drand48(void);
+double   erand48(unsigned short[3]);
+long     jrand48(unsigned short[3]);
+void     lcong48(unsigned short[7]);
+long     lrand48(void);
+long     mrand48(void);
+long     nrand48(unsigned short[3]);
+long     random(void);
+int      rand_r(unsigned *);
+
+void test_rand()
+{
+  unsigned short a[7];
+  unsigned b;
+  
+  rand();	// no-warning
+  drand48();	// no-warning
+  erand48(a);	// no-warning
+  jrand48(a);	// no-warning
+  lcong48(a);	// no-warning
+  lrand48();	// no-warning
+  mrand48();	// no-warning
+  nrand48(a);	// no-warning
+  rand_r(&b);	// no-warning
+  random();	// no-warning
+}