Add information about vcl object instances to the panic output

In the absence of a core dump, we do not have any information yet in the
panic output about vcl object instances, for example to find out which
object a priv belongs to when the instance address is used for
per-instance priv state.

To make this information available at the time of a panic, we add the
following:

* A struct vrt_ii (for instance info), of which a static gets
  filled in by VCC to contain the pointers to the C global variable
  instance pointers at VCC time

* A pointer to this struct from the VCL_conf to make it available to
  the varnishd worker

* dumps of the instance info for panics

bin/varnishd/cache/cache_vcl.c

@@ -44,6 +44,7 @@
 #include "cache_vcl.h"
 #include "vcli_serve.h"
 #include "vtim.h"
+#include "vcc_interface.h"
 
 const struct vcltemp VCL_TEMP_INIT[1] = {{ .name = "init", .is_cold = 1 }};
 const struct vcltemp VCL_TEMP_COLD[1] = {{ .name = "cold", .is_cold = 1 }};
@@ -208,6 +209,7 @@ vcl_find(const char *name)
 void
 VCL_Panic(struct vsb *vsb, const char *nm, const struct vcl *vcl)
 {
+	const struct vpi_ii *ii;
 	int i;
 
 	AN(vsb);
@@ -233,6 +235,15 @@ VCL_Panic(struct vsb *vsb, const char *nm, const struct vcl *vcl)
 		for (i = 0; i < vcl->conf->nsrc; ++i)
 			VSB_printf(vsb, "\"%s\",\n", vcl->conf->srcname[i]);
 		VSB_indent(vsb, -2);
+		VSB_cat(vsb, "instances = {\n");
+		VSB_indent(vsb, 2);
+		ii = vcl->conf->instance_info;
+		while (ii != NULL && ii->p != NULL) {
+			VSB_printf(vsb, "\"%s\" = %p,\n", ii->name,
+			    (const void *)*(const uintptr_t *)ii->p);
+			ii++;
+		}
+		VSB_indent(vsb, -2);
 		VSB_cat(vsb, "},\n");
 	}
 	VSB_indent(vsb, -2);

bin/varnishtest/tests/v00010.vtc

@@ -26,6 +26,12 @@ server s1 {
 
 varnish v1 -arg "-sdefault,1m" -vcl+backend {
 	import vtc;
+	import debug;
+
+	sub vcl_init {
+		new foo = debug.obj("foo");
+		new bar = debug.concat("bar");
+	}
 
 	sub vcl_backend_response {
 		if (beresp.http.panic == "fetch") {

include/vcc_interface.h

@@ -64,5 +64,11 @@ struct vrt_acl {
 	const char	*name;
 };
 
+/* vmod object instance info */
+struct vpi_ii {
+	const void *			p;
+	const char * const		name;
+};
+
 VCL_STRANDS VPI_BundleStrands(int, struct strands *, char const **,
     const char *f, ...);

lib/libvcc/generate.py

@@ -656,6 +656,7 @@ struct VCL_conf {
 	const char		**srcbody;
 
 	int			nvmod;
+	const struct vpi_ii	*instance_info;
 
 	vcl_event_f		*event_vcl;
 """)

lib/libvcc/vcc_compile.c

@@ -488,6 +488,7 @@ EmitStruct(const struct vcc *tl)
 #define VCL_MET_MAC(l,u,t,b) \
 	Fc(tl, 0, "\t." #l "_func = VGC_function_vcl_" #l ",\n");
 #include "tbl/vcl_returns.h"
+	Fc(tl, 0, "\t.instance_info = VGC_instance_info\n");
 	Fc(tl, 0, "};\n");
 }
 
@@ -711,6 +712,8 @@ vcc_CompileSource(struct vcc *tl, struct source *sp, const char *jfile)
 
 	EmitInitFini(tl);
 
+	VCC_InstanceInfo(tl);
+
 	EmitStruct(tl);
 
 	VCC_XrefTable(tl);

lib/libvcc/vcc_compile.h

@@ -398,6 +398,7 @@ sym_act_f vcc_Act_New;
 
 /* vcc_xref.c */
 int vcc_CheckReferences(struct vcc *tl);
+void VCC_InstanceInfo(struct vcc *tl);
 void VCC_XrefTable(struct vcc *);
 
 void vcc_AddCall(struct vcc *, struct token *, struct symbol *);

lib/libvcc/vcc_xref.c

@@ -317,6 +317,29 @@ vcc_xreftable_len(struct vcc *tl, const struct symbol *sym)
 		sym_type_len = len;
 }
 
+static void v_matchproto_(symwalk_f)
+vcc_instance_info(struct vcc *tl, const struct symbol *sym)
+{
+
+	CHECK_OBJ_NOTNULL(sym, SYMBOL_MAGIC);
+	CHECK_OBJ_NOTNULL(sym->kind, KIND_MAGIC);
+	if (sym->kind != SYM_INSTANCE)
+		return;
+	AN(sym->rname);
+	Fc(tl, 0, "\t{ .p = &%s, .name = \"", sym->rname);
+	VCC_SymName(tl->fc, sym);
+	Fc(tl, 0, "\" },\n");
+}
+
+void
+VCC_InstanceInfo(struct vcc *tl)
+{
+	Fc(tl, 0, "\nconst struct vpi_ii VGC_instance_info[] = {\n");
+	VCC_WalkSymbols(tl, vcc_instance_info, SYM_NONE);
+	Fc(tl, 0, "\t{ .p = NULL, .name = \"\" }\n");
+	Fc(tl, 0, "};\n");
+}
+
 static void v_matchproto_(symwalk_f)
 vcc_xreftable(struct vcc *tl, const struct symbol *sym)
 {