• Nils Goroll's avatar
    vcc: Expand SUB type, add possible calling methods · bba4b145
    Nils Goroll authored
    Until now, the VCC SUB type represented the literal name of a
    vcc-generated C function, which was used to expand the VCL "call"
    action.
    
    We now add a struct to describe VCL subs and calculate a bitmask which
    represents the bilt-in subs which a SUB may be called from (the
    "okmask"),
    
    This is in preparation of the goal to add a VCL_SUB vmod type which
    will allow VMODs to call into vcl subs.
    
    We add to the vcl shared object a struct vcl_sub for each sub, which
    contains:
    
    	- a methods bitmask defining which built-in subs this sub may
    	  be called from (directly or indirectly)
    	- the name as seen from vcl
    	- a pointer back to the VCL_conf
    	- the function pointer to the vcl_func_f
    	- a unique number
    
    About the methods bitmask:
    
    It contains the VCL_MET_* bits of of built-in subs (traditionally
    called methods) which are allowed to call this sub.
    
    It is intended for checks like
    
    	if (sub->methods & ctx->method) {
    		sub->func(ctx);
    		return;
    	} else {
    		VRT_fail(ctx, "not allowed here");
    		return;
    	}
    
    In existing compile-time calls, we already check if used objects and
    returned actions are allowed within the respective calling context.
    
    To build the methods bitmask, we begin with a VCL_MET_TASK_ALL
    bitfield and clear the bits of methods which would not be allowed for
    any used object or returned action.
    
    About the VCL_conf pointer:
    
    Each VCL SUB belongs to a VCL, this pointer will allow to check that
    it is only ever used from the right VCL.
    
    About the unique number:
    
    By numbering vcl subs (per VCL), we can later implement a recursion
    check using a bitmask.
    
    In struct VCL_conf, we record the total number of subs.
    bba4b145
generate.py 21.2 KB