C++ on Intel vs. M1/M2

2024-04-16 15:25 UTC gpt-4 Open in ChatGPT ↗

You

Are there differences when running c++ in intel macs versus in M1 or M2 macs?

ChatGPT

Yes, there are differences when running C++ code on Intel Macs compared to M1 or M2 Macs, primarily due to the underlying processor architectures and the associated toolchains.

1. Processor Architecture:

   • Intel Macs: These use x86-64 architecture processors. C++ applications and other software written for Intel Macs are optimized for this architecture.
   • M1/M2 Macs: These feature Apple’s own ARM-based architecture. ARM processors are known for their efficiency and performance per watt, which differs from the architecture of Intel processors.

2. Compilation and Optimization:

   • C++ code needs to be compiled specifically for the architecture it will run on. For M1 and M2 Macs, developers need to ensure that their code is compiled for ARM architecture. This can involve using different compiler flags, optimizations, and sometimes even modifying the code to take advantage of ARM-specific features.
   • Apple provides Universal Binaries support, which allows applications to include both x86-64 and ARM versions of the code. This way, the same binary can run on both Intel and Apple Silicon Macs.

3. Performance Considerations:

   • The ARM architecture used in M1 and M2 Macs can lead to differences in performance due to its design. For instance, ARM processors may perform better in energy efficiency and thermal management, which can affect sustained performance.
   • Specific optimizations in the ARM architecture, like the use of big.LITTLE technology in CPU design, can lead to improvements in how efficiently tasks are processed.

4. Toolchain and Ecosystem:

   • Developers must use a toolchain that supports ARM architecture when developing for M1 or M2 Macs. Apple’s Xcode and command line tools have been updated to support ARM, including the LLVM-based compiler that supports both architectures.
   • Some third-party tools and libraries may still be in the process of being optimized or ported to ARM, which can affect development and performance.

5. Software Compatibility:

   • Software compatibility is also a consideration. Applications not yet optimized for ARM may run through Rosetta 2, a translation layer that allows x86-64 applications to run on ARM architecture. While effective, running applications through Rosetta 2 can incur a performance penalty compared to native ARM apps.

In practice, for C++ developers, this means testing and potentially adapting their code for compatibility and performance on M1 and M2 Macs. Moreover, ongoing updates from Apple and third-party library vendors will continue to enhance support for the ARM architecture in macOS.

You

I am compiling a dylib library that I am then importing in VBA for excel and for some reason it doesn’t work the same in m1 and intel macs. Specifically, while all features work for m1 the intel macs excel file crashes . The function i am interested in sends a byte array to VBA. Any ideas?

ChatGPT

Dealing with issues where a dylib library works differently on Intel Macs compared to M1 or M2 Macs, especially when integrating with VBA for Excel, can be complex due to multiple layers of software and hardware interactions. Here are a few areas to consider and investigate to resolve the issue where your Excel file crashes on Intel Macs but works fine on M1 or M2 Macs:

1. Architecture-Specific Builds

• Universal Binary: Ensure that your dylib is compiled as a Universal Binary containing code for both x86_64 (Intel) and ARM64 (Apple Silicon). This ensures that the correct code is executed on the respective architecture.
• Separate Builds: Alternatively, you could compile two separate versions of your dylib, one for each architecture, to isolate and ensure that each is optimized and functioning correctly for its respective processor.

2. Debugging and Logging

• Debug Build: Compile a debug version of your dylib with extensive logging around the function in question. Check for any errors or unusual behavior specifically when handling the byte array.
• Memory Management: Pay close attention to memory allocation and boundary conditions. Mismanagement in memory handling can often lead to crashes, especially when interfacing with another language like VBA.

3. Data Type Compatibility

• Byte Array Handling: Ensure that the way the byte array is managed and transferred between C++ and VBA is compatible with both architectures. Differences in data alignment, endianness, or size of data types could be causing issues on the Intel architecture.
• Interface Boundaries: Verify that the ABI (Application Binary Interface) conventions are correctly adhered to, including calling conventions, stack cleanup, and parameter passing.

4. Excel and VBA Environment

• Version of Excel: Check if the versions of Excel for Mac on Intel and M1/M2 are the same. Sometimes, differences in Excel versions or updates can cause compatibility issues.
• Excel’s Error Logs: Look for any logs or error messages generated by Excel on the Intel Macs which could give more specific clues as to why it’s crashing.

5. Testing and Validation

• Unit Testing: If possible, unit test the function or sections of the dylib independently from Excel to ensure they work as expected on both architectures.
• Cross-Platform Testing Tools: Utilize tools that can simulate or emulate different architectures to test your library without needing physical machines.

6. Use of External Libraries or Dependencies

• Dependencies: If your dylib depends on other libraries, ensure they are also compiled for both architectures or are not causing conflicts due to architecture-specific issues.

7. Compiler and Build Tools

• Compiler Flags: Review the compiler and linker flags being used. Specific flags may be needed to handle architecture differences correctly, especially concerning optimizations and architecture-specific instructions.

By methodically checking these areas, you can better isolate the cause of the crash on Intel Macs. If the issue persists, consider using tools like gdb or lldb for more in-depth debugging, potentially attaching the debugger to Excel when it loads the dylib to catch the crash in action.

You

Where are excel error logs? How can i access them?

ChatGPT

Microsoft Excel for Mac doesn’t generate a detailed error log in the same way some other applications might, such as those running on Windows. However, there are still a few ways you can try to diagnose issues like crashes:

1. Console Application

The macOS Console application can be a useful tool to view system logs that might contain information about application crashes, including Excel:

• Open Console: You can find the Console application in the Applications > Utilities folder. Launch it.
• Filter for Excel: In the Console app, use the search bar at the top right to type “Excel” to filter out logs related specifically to Microsoft Excel.
• Look for Crash Logs: Pay particular attention to any crash reports or error messages that occur around the time of the Excel crash.

2. System Reports

Crash reports specifically are usually found in the Library/Logs/DiagnosticReports folder, which can be accessed using the Finder:

• Open Finder.
• Go to Folder: In the Finder menu, choose Go > Go to Folder.
• Type in Path: Enter ~/Library/Logs/DiagnosticReports and press Enter.
• Search for Excel Reports: Look for files that might be named similarly to Microsoft Excel_2023-04-15-123456_MacBook-Pro.crash.

3. Microsoft Error Reporting

When an application like Excel crashes, you might see Microsoft’s error reporting tool prompt you to send data about the crash to Microsoft. This tool sometimes provides an error code or a brief description of the problem, which can be useful for troubleshooting:

• Details of Error: When prompted by the error reporting tool after a crash, look for any detailed information it might provide.
• Copy or Take Note: You can copy this information for further research or to provide details to support forums or technical support.

4. Activity Monitor for Hangs

If Excel doesn’t crash but hangs or becomes unresponsive, using Activity Monitor might provide some clues:

• Open Activity Monitor: Found in Applications > Utilities.
• Find Excel: Look for Excel in the list of processes.
• Sample Process: If Excel is unresponsive, you can select it and use the gear icon in the toolbar to choose Sample Process. This will generate a report that could help identify what Excel is doing at that time.

5. Check for Updates

Sometimes, issues are known bugs that get fixed in updates, so ensure your version of Excel and macOS are fully updated.

6. VBA Debugging

If you suspect the issue is related to your VBA macro or the interaction with your dylib:

• Use VBA Debugger: Open the VBA editor in Excel (using Tools > Macro > Visual Basic Editor), set breakpoints, and step through the code to see where it might be failing.

These methods should help you gather more information about what might be causing Excel to crash when using your dylib on Intel Macs.