Fixes segfault when reading from an empty source

README.md

@@ -354,7 +354,7 @@ using namespace libzippp;
 
 int main(int argc, char** argv) {
   //important to use calloc/malloc for the fromWritableBuffer !
-  char* buffer = (char*)calloc(4096, sizeof(char));
+  void* buffer = calloc(4096, sizeof(char));
 
   ZipArchive* z1 = ZipArchive::fromWritableBuffer(&buffer, 4096, ZipArchive::New);
   /* add content to the archive */

src/libzippp.cpp

@@ -109,8 +109,12 @@ namespace Helper {
     }
 
     static void callErrorHandlingCallback(zip* zipHandle, const std::string& msg, ErrorHandlerCallback* callback) {
-        zip_error_t* error_code = zip_get_error(zipHandle);
-        callErrorHandlingCallbackFunc(error_code->str, error_code->zip_err, error_code->sys_err, callback);
+        if(zipHandle!=nullptr) {
+            zip_error_t* error_code = zip_get_error(zipHandle);
+            callErrorHandlingCallbackFunc(error_code->str, error_code->zip_err, error_code->sys_err, callback);
+        } else {
+            callErrorHandlingCallbackFunc("", -1, -1, callback);
+        }
     }
 
     static void callErrorHandlingCallback(zip_error_t* error, const std::string& msg, ErrorHandlerCallback* callback) {
@@ -433,7 +437,7 @@ int ZipArchive::close(void) {
                 *bufferData = sourceBuffer;
                 bufferLength = totalRead;
             } else {
-                Helper::callErrorHandlingCallback(zipHandle, "can't read back from source: changes were not pushed in the buffer\n", errorHandlingCallback);
+                Helper::callErrorHandlingCallback((zip*)nullptr, "can't read back from source: changes were not pushed in the buffer\n", errorHandlingCallback);
                 return LIBZIPPP_ERROR_HANDLE_FAILURE;
             }
 

tests/tests.cpp

@@ -894,6 +894,34 @@ void test23() {
     }*/
 }
 
+void test23_2() {
+    //important to use calloc/malloc for the fromWritableBuffer !
+    void* buffer = calloc(4096, sizeof(char));
+
+    ZipArchive* z1 = ZipArchive::fromWritableBuffer(&buffer, 4096, ZipArchive::New);
+    /* add content to the archive */
+
+    //will update the content of the buffer
+    z1->close();
+
+    //length of the buffer content
+    int bufferContentLength = z1->getBufferLength();
+
+    ZipArchive::free(z1);
+
+    //read again from the archive:
+    ZipArchive* z2 = ZipArchive::fromBuffer(buffer, bufferContentLength);
+    /* read the archive - no modification allowed */
+    ZipArchive::free(z2);
+
+    //read again from the archive, for modification:
+    ZipArchive* z3 = ZipArchive::fromWritableBuffer(&buffer, bufferContentLength);
+    /* read/write the archive */
+    ZipArchive::free(z3);
+
+    free(buffer);
+}
+
 static void myErrorHandler(const std::string& message,
                            const std::string& strerror,
                            int zip_error_code,
@@ -920,7 +948,7 @@ int main() {
     test6();  test7();  test8();  test9();  test10();
     test11(); test12(); test13(); test14(); test15();
     test16(); test17(); test18(); test19(); test20();
-    test21(); test22(); test23(); test24();
+    test21(); test22(); test23(); test23_2(); test24();
     return 0;
 }