Thanks to one and all for this AMA! The massive number of comments testifies to the continuing interest in C, and I think we're all grateful to all of you for your expertise, your patience, and your even-handed responses.
1. define a highly-extensible abstraction model, which implementations intended for various purposes should be expected to extend to suit those purpose, or
2. define an abstraction model which is sufficiently complete that programs can do everything that would need to be done, without need for extensions?
Reading the C89 and C99 Rationale documents, it's clear that those standards were intended to meet the former purpose. The way some compilers treat "Undefined Behavior", however, suggests that the maintainers view the Standard as aimed toward the latter purpose.
During the 1980s and 1990s, it was generally cheaper and easier for implementations to extend the Standard's abstraction model by specifying that many actions would be processed "in a documented fashion characteristic of the environment" than it would have been to do anything else, so there was no need to worry about whether the Standard allowed programmers to specify when such behavior was required. That no longer holds true, however.
While it would be reasonable to deprecate code which relies upon such treatment without explicitly demanding it, such deprecation would only make sense if there were a means of demanding such treatment when required. For the Committee to provide such means, however, it would have to reach a consensus as to the purposes for which the Standard's abstraction model is meant to be suitable. Are you aware of any such consensus?
1. define a highly-extensible abstraction model, which implementations intended for various purposes should be expected to extend to suit those purpose, or
2. define an abstraction model which is sufficiently complete that programs can do everything that would need to be done, without need for extensions?
Reading the C89 and C99 Rationale documents, it's clear that those standards were intended to meet the former purpose. The way some compilers treat "Undefined Behavior", however, suggests that the maintainers view the Standard as aimed toward the latter purpose.
During the 1980s and 1990s, it was generally cheaper and easier for implementations to extend the Standard's abstraction model by specifying that many actions would be processed "in a documented fashion characteristic of the environment" than it would have been to do anything else, so there was no need to worry about whether the Standard allowed programmers to specify when such behavior was required. That no longer holds true, however.
While it would be reasonable to deprecate code which relies upon such treatment without explicitly demanding it, such deprecation would only make sense if there were a means of demanding such treatment when required. For the Committee to provide such means, however, it would have to reach a consensus as to the purposes for which the Standard's abstraction model is meant to be suitable. Are you aware of any such consensus?