> Here's what happens, over the years, to such code:
Over how many years? Some of my projects are 30+ years old and support a few dozen combinations of OSes, compilers, and architectures, and the method I described hasn't led to a rat's nest yet.
> #ifdef's on the wrong feature. For example, #ifdef on operating system for a CPU feature
Sure, same thing happens when you decide whether to compile in your stubs or not. But if I make a mistake, the code usually won't compile on the configuration in question; if you make a similar mistake, it'll compile with your stub, it might even link, but you'll get odd runtime behavior. Sounds worse.
> Overly complex #if expressions, that steadily get worse
All code gets worse over time and bit rots if you don't maintain it, I don't see things necessarily worse in this area.
> Fixing support for X that subtlety breaks F and Q support. It goes unnoticed because your build/test machines are not F and Q
If you aren't testing on tier one configurations, they shouldn't be tier one. And if a tier three configuration breaks when you do finally get around to testing it, it's tier three, so it gets fixed when it can be and there's no problem. Similar to normal code, I'd say.
> People having no idea what #defines to set on the command line, nor what the ones that are set are doing (if anything)
> People having no idea how to fold in support for new configurations
These problems exist for normal code as well. Someone has to own the build configurations, and they have to be maintained, like anything else.
> Code will #ifdef on predefined macros that have little or no documentation on what they're for or under exactly what circumstances they are set. If the writer even bothered to research that. gcc predefines what, 400 macros?
We only use a handful, and they are fairly well documented. But even if they weren't, since the code works on all tier one platforms, we'd know if something was changed out from underneath us because it was underspecified or accidentally relied upon.
But again the same can happen with normal code and system headers, compiler extensions, etc - I don't see why pre-processor macros have to be singled out here.
Over how many years? Some of my projects are 30+ years old and support a few dozen combinations of OSes, compilers, and architectures, and the method I described hasn't led to a rat's nest yet.
> #ifdef's on the wrong feature. For example, #ifdef on operating system for a CPU feature
Sure, same thing happens when you decide whether to compile in your stubs or not. But if I make a mistake, the code usually won't compile on the configuration in question; if you make a similar mistake, it'll compile with your stub, it might even link, but you'll get odd runtime behavior. Sounds worse.
> Overly complex #if expressions, that steadily get worse
All code gets worse over time and bit rots if you don't maintain it, I don't see things necessarily worse in this area.
> Fixing support for X that subtlety breaks F and Q support. It goes unnoticed because your build/test machines are not F and Q
If you aren't testing on tier one configurations, they shouldn't be tier one. And if a tier three configuration breaks when you do finally get around to testing it, it's tier three, so it gets fixed when it can be and there's no problem. Similar to normal code, I'd say.
> People having no idea what #defines to set on the command line, nor what the ones that are set are doing (if anything) > People having no idea how to fold in support for new configurations
These problems exist for normal code as well. Someone has to own the build configurations, and they have to be maintained, like anything else.
> Code will #ifdef on predefined macros that have little or no documentation on what they're for or under exactly what circumstances they are set. If the writer even bothered to research that. gcc predefines what, 400 macros?
We only use a handful, and they are fairly well documented. But even if they weren't, since the code works on all tier one platforms, we'd know if something was changed out from underneath us because it was underspecified or accidentally relied upon.
But again the same can happen with normal code and system headers, compiler extensions, etc - I don't see why pre-processor macros have to be singled out here.
> Jyust yew wite, 'enry 'iggins, jyust yew wite!
How long?