select_stdlib_config.hpp including <version> vs <VERSION> on OS X

From: Allen Sanderson (allen_at_[hidden])
Date: 2021-04-08 17:55:31

Hello, 

A casual boost user and abuser here. Some specifics on my OS 

OS X Big Sur 11.2 

Xcode 12.4 

Compiler clang : Apple land version 12.0.0 

Boost 1.73 - forward 

When select_stdlib_config.hpp is included it gets to this initial code to include <version>

... 
#if defined(__cplusplus) && defined(__has_include) 
# if __has_include(<version>) 
// It should be safe to include `<version>` when it is present without checking 
// the actual C++ language version as it consists solely of macro definitions. 
// [version.syn] p1: The header <version> supplies implementation-dependent 
// information about the C++ standard library (e.g., version number and release date). 
# include <version> 
... 

The issue is that many projects (gnuplot, builtbot, and others) have a VERSION file in their top level src directory. On a traditional Linux system the case sensitivity would make sure the right file is included. However, many/most OS X file systems are case insensitive. As such, the project's VERSION file gets included instead. And does not compile. 

I have no solution to the issue other than I renamed our project’s VERSION file for the time being. However, I wanted to raise the issue as I noticed it when moving to 1.75 and backtracked out that it was a recent changed starting with boost 1.73

Cheers, 
Allen Sanderson 
SCI Institute 
University of Utah