[cfe-dev] Delay Clang CodeGen until AST is fully populated

[Alexandre Isoard via cfe-dev]

Hello,

We are having issues with modifying the Clang AST while it is being built,
and we suspect they are due to it being code generated before it is fully
populated, and *we were wondering if it was possible to require the Sema to
be fully finished before doing any CodeGen?*

An example would be when we process custom pragma:

int my_global;

int my_function() {
    my_global = 1;
}

int main() {
#pragma FOO SOMETHING var=my_global
    my_function();
    return 0;
}


Here the way I process the pragma is that it attach to the AST node for
my_global, an attribute node. So that once I code-generate that global
variable I can "do something" based on that attribute. Unfortunately, today
Clang might codegen that global as soon as it deem it necessary (typically,
when code-generating my_function as it uses it). And the pragma has not yet
been semantically parsed yet.

If I were to use -ast-print and dump the result into a file, then the
attribute would be there, and if I parse that file again I would get the
correct codegen. But I assume it is unsafe to rely on being able to parse
-ast-print and/or it's AST to be the same.

Any input on that issue?

-- 
*Alexandre Isoard*
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