[ECOS] compiler dependencies
Tue Dec 22 07:02:00 GMT 1998
>>>>> "Kenneth" == Kenneth Porter <firstname.lastname@example.org> writes:
>> eCos makes use of a number of very useful language extensions
>> which are provided by gcc and g++ but not by other compilers,
>> and there are no plans to support other compilers.
Kenneth> Can you enumerate these in the FAQ? I see two listed,
Kenneth> priority constructor ordering (required) and selective
Kenneth> linking (optional).
I have now added a section to the FAQ related to this. Please see
Kenneth> I've been using Borland's compiler for some time in the
Kenneth> PC 16-bit world and in embedded system development and I
Kenneth> know it supports a generalization of priority constructor
Kenneth> ordering: One can use "#pragma startup" with a priority
Kenneth> code to request that a function be executed during RTL
Kenneth> init. The RTL uses this mechanism to order initialization
Kenneth> of various RTL structures (heap, stdio, FPU emulator).
Kenneth> The compiler uses the same internal structures to
Kenneth> implement constructor calls for static objects.
#pragma is usually a poor choice for doing this sort of thing. The gcc
documentation includes the following in the description of
> Some people object to the `__attribute__' feature, suggesting that
> ANSI C's `#pragma' should be used instead. There are two reasons for
> not doing this.
> 1. It is impossible to generate `#pragma' commands from a macro.
> 2. There is no telling what the same `#pragma' might mean in
> another compiler.
> These two reasons apply to almost any application that might be
> proposed for `#pragma'. It is basically a mistake to use `#pragma'
> for *anything*.
There is some work in progress in the ISO C standard world to come up
with something like #pragma but without these shortcomings. Until that
becomes widely available it is not possible to use #pragma safely in
Bart Veer // eCos net maintainer
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