Resumable Assert

Assert replacement to continue execution in debugger

In any large app, it sometimes happens that some asserts are failing in code you don't currently care about, and blocking the entire team from being able to run the app until the issue is fixed is not the best workflow. So we usually end up moving the execution marker past the assert line in IDE or debugger, or even comment the assert out, recompile and relaunch. With Resumable Assert, you can simply continue execution when an assertion fails in debugger, or even disable asserts that you are not interested in, so that those never bother you again.

Disclaimer: be careful with that power though, since execution of potentially broken code may lead to unrecoverable errors in future.

C/C++/Objective-C

First, include or import the header:

#import "ResumableAssert.h"

Then, use the RESUMABLE_ASSERT() or RESUMABLE_ASSERT_WITH_FORMAT() macros instead of the standard ones: assert(), NSAssert(), etc.

Once RESUMABLE_ASSERT() variant is hit in debug mode, you can ignore it and continue execution, or disable it permanently, or even disable all asserts permanently with corresponding lldb commands when prompted.

For example, the following assert somewhere in ViewController.viewDidLoad method:

RESUMABLE_ASSERT(2 + 2 == 5);

Or:

RESUMABLE_ASSERT_WITH_FORMAT(2 + 2 == 5, "Calculation error");

Leads to the following debugger console output:

ViewController.m:-[ViewController viewDidLoad]:42
Assertion failed: 2 + 2 == 5
Calculation error
Continue execution or issue one of the following lldb commands:
e disable = 1  # disable this assert permanently
e unleash = 1  # disable all asserts permanently

Where you can just continue execution, or additionally disable the assert:

(lldb) e disable = 1
(volatile int) $1 = 1
(lldb) c
Process 11193 resuming

Custom logging

RESUMABLE_ASSERT() macro in C uses stdout to print the failure message by default. To change this behavior and use something else for logging, (e.g. NSLog()) redefine the RESUMABLE_ASSERT_LOG() macro in C like so:

#import <Foundation/Foundation.h>

#include "ResumableAssert.h"

#undef RESUMABLE_ASSERT_LOG
#define RESUMABLE_ASSERT_LOG(condition, format, ...)                 \
  do {                                                               \
    NSLog(@"%s:%u\nAssertion failed: %s\n" format,                   \
          __PRETTY_FUNCTION__, __LINE__, condition, ##__VA_ARGS__);  \
  } while (0)

Similarly, you can define your own assert macro with a custom name:

#define ASSERT_WITH_FORMAT(condition, format, ...) \
  RESUMABLE_ASSERT_WITH_FORMAT(condition, format, ##__VA_ARGS__)
#define ASSERT(condition) ASSERT_WITH_FORMAT(condition, "")

Swift

For Swift and other languages, we provide ResumableAssertDebugTrap() function that implements the core logic of resumable assert. You can then implement a custom assert() function somewhere in a custom Diagnostics module which would use ResumableAssertDebugTrap() internally:

import ResumableAssert // Import the module or use a bridging header and import ResumableAssert.h.

public func assert(
  _ condition: @autoclosure () -> Bool,
  _ message: @autoclosure () -> String = "",
  file: StaticString = #file,
  function: StaticString = #function,
  line: UInt = #line
) {
#ifdef DEBUG
  if !condition() {
    NSLog("Assertion failed:" + " \(message()):" +
          " file \(file.description), function \(function.description), line \(line)")
    ResumableAssertDebugTrap()
  }
#endif
}

Then, you can use the new function as:

Diagnostics.assert(2 + 2 == 5, "Calculation error")

Setup

Bazel

In your BUILD file, add ResumableAssert deps to corresponding targets:

objc_library(
  # ...
  deps = [
    "//path/to/ResumableAssert",
  ],
  # ...
)

Include or import the header:

#import "path/to/ResumableAssert/ResumableAssert.h"

CocoaPods

To use ResumableAssert for Objective-C, add the following to your Podfile:

pod 'ResumableAssert', '~> 1.0'

Then, run pod install and import the umbrella header in generated project:

#import <ResumableAssert/ResumableAssert.h>

Or, the module:

@import ResumableAssert;