Revert using __builtin_dump_struct as a fallback to print object description

This call is unsafe and cannot be made safe unfortunately.

Author: gershnik

CHANGELOG.md

@@ -5,9 +5,6 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## Unreleased
 
-### Changed
-- `XCTestUtil.h`: default output for printing C++ objects changed to use [`__builtin_dump_struct`](https://clang.llvm.org/docs/LanguageExtensions.html#builtin-dump-struct) clang intrinsic.
-
 ## [3.0] - 2024-01-17
 
 ### Changed

README.md

@@ -349,7 +349,7 @@ That, in the case of failure, try to obtain description using the following meth
 - If there is an ADL call `testDescription(obj)` that produces `NSString *`, use that.
 - Otherwise, if there is an ADL call `to_string(obj)` in `using std::to_string` scope, use that
 - Otherwise, if it is possible to do `ostream << obj`, use that
-- Finally produce use the output of [`__builtin_dump_struct`](https://clang.llvm.org/docs/LanguageExtensions.html#builtin-dump-struct) clang intrinsic.
+- Finally produce `"<full name of the type> object"` string.
 
 Thus if an object is printable using the typical means those will be automatically used. You can also make your own objects printable using either of the means above. The `testDescription` approach specifically exists to allow you to print something different for tests than in normal code.
 

include/objc-helpers/XCTestUtil.h

@@ -18,8 +18,7 @@
 #import <XCTest/XCTest.h>
 
 #include <sstream>
-#include <string>
-#include <stdarg.h>
+#include <cxxabi.h>
 
 namespace TestUtil {
     using std::to_string;
@@ -41,21 +40,14 @@ namespace TestUtil {
         { str << obj };
     };
 
-    auto sprintf(std::string & res, const char * format, ...) -> int {
-        va_list vl;
-        va_start(vl, format);
-        const int size = vsnprintf(0, 0, format, vl);
-        va_end(vl);
-        if (size <= 0)
-            return size;
-        size_t appendPos = res.size();
-        size_t appendSize = size_t(size) + 1;
-        res.resize(appendPos + appendSize);
-        va_start(vl, format);
-        const int ret = vsnprintf(&res[appendPos], appendSize, format, vl);
-        va_end(vl);
-        res.resize(appendPos + size_t(ret > 0 ? ret : 0));
-        return ret;
+    inline auto demangle(const char * name) -> std::string {
+
+        int status = 0;
+        std::unique_ptr<char, void(*)(void*)> res {
+            abi::__cxa_demangle(name, nullptr, nullptr, &status),
+            std::free
+        };
+        return (status==0) ? res.get() : name ;
     }
 
     template<class T>
@@ -72,9 +64,7 @@ namespace TestUtil {
             str << val;
             return @(str.str().c_str());
         } else {
-            std::string res;
-            __builtin_dump_struct(&val, sprintf, res);
-            return @(res.c_str());
+            return [NSString stringWithFormat:@"%s object", demangle(typeid(T).name()).c_str()];
         }
     }
 }

test/XCTestUtilTests.mm

@@ -173,7 +173,7 @@ void _XCTFailureHandler(XCTestCase * _Nullable test, BOOL expected, const char *
 TEST_CASE( "Generic" ) {
     failures.clear();
     XCTAssertCppEqual(bar{1}, bar{2});
-    CHECK_FAILURE(__LINE__ - 1, true, "((bar{1}) equal to (bar{2})) failed: (\"(anonymous namespace)::bar {\n  int i = 1\n}\n\") is not equal to (\"(anonymous namespace)::bar {\n  int i = 2\n}\n\")", "");
+    CHECK_FAILURE(__LINE__ - 1, true, "((bar{1}) equal to (bar{2})) failed: (\"(anonymous namespace)::bar object\") is not equal to (\"(anonymous namespace)::bar object\")", "");
 }
 
 namespace {