test overriding a local function

tests/CMakeLists.txt

@@ -1,6 +1,11 @@
+# Copyright (c) Lysann Tranvouez.  All rights reserved.
+
 add_executable(mach_detours_tests
         test.cpp)
 
+# The target function must be in a shared library because otherwise it might be in the same code page as the test.cpp functions.
+# Between attach and commit the target function's code page is not executable, which can mean our test driver code would not
+# be executable.
 add_library(mach_detours_test_func SHARED
         test_func.c
         test_func.h

tests/test.cpp

@@ -4,6 +4,8 @@
 
 #include <mach_detours.h>
 
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
 #include "test_func.h"
 
 static int testFunctionDetourCounter = 0;
@@ -13,7 +15,7 @@ int testFunctionDetour()
     return 94;
 }
 
-TEST_CASE( "Overriding custom function" )
+TEST_CASE( "Overriding custom function in dylib" )
 {
     int (*realTestFunction)() = testFunction;
     testFunctionCounter = 0;
@@ -35,3 +37,43 @@ TEST_CASE( "Overriding custom function" )
     REQUIRE( testFunctionCounter == 1 );
     REQUIRE( testFunctionDetourCounter == 1 );
 }
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+static int localFunctionCounter = 0;
+int localFunction()
+{
+    localFunctionCounter++;
+    return 67;
+}
+static int localFunctionDetourCounter = 0;
+int localFunctionDetour()
+{
+    localFunctionDetourCounter++;
+    return 12;
+}
+
+TEST_CASE( "Overriding local function" )
+{
+    int (*realFunction)() = localFunction;
+    localFunctionCounter = 0;
+    localFunctionDetourCounter = 0;
+
+    REQUIRE( localFunction() == 67 );
+    REQUIRE( localFunctionCounter == 1 );
+    REQUIRE( localFunctionDetourCounter == 0 );
+
+    CHECK( detour_transaction_begin() == err_none );
+    // Overriding a local function requires using detour_attach_and_commit instead of calling attach and commit individually.
+    // Otherwise when we return from attach (and before commit), the code page with the local function is marked as read+write (but _not_ executable).
+    // There is a good chance the code we return to (in this case the test function) is on the same memory page and can therefore not be executed (until we call commit).
+    CHECK( detour_attach_and_commit(reinterpret_cast<detour_func_t*>(&realFunction), reinterpret_cast<detour_func_t>(localFunctionDetour)) == err_none );
+
+    REQUIRE( realFunction != localFunction );
+
+    REQUIRE( localFunctionCounter == 1 );
+    REQUIRE( localFunctionDetourCounter == 0 );
+    REQUIRE( localFunction() == 12 );
+    REQUIRE( localFunctionCounter == 1 );
+    REQUIRE( localFunctionDetourCounter == 1 );
+}

tests/test_func.c

@@ -1,3 +1,5 @@
+// Copyright (c) Lysann Tranvouez.  All rights reserved.
+
 #include "test_func.h"
 
 int testFunctionCounter = 0;

tests/test_func.h

@@ -1,3 +1,5 @@
+// Copyright (c) Lysann Tranvouez.  All rights reserved.
+
 #pragma once
 
 #ifdef __cplusplus