[wasm] Change the constant kV8MaxWasmMemoryPages to a command line flag.

src/flag-definitions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file defines all of the flags.  It is separated into different section,
 // for Debug, Release, Logging and Profiling, etc.  To add a new flag, find the
 // correct section, and use one of the DEFINE_ macros, without a trailing ';'.
 //
 // This include does not have a guard, because it is a template-style include,
 // which can be included multiple times in different modes.  It expects to have
@@ skipping 481 matching lines @@
             "simplifies execution model to make porting "
             "easier (e.g. always use Ignition, never use Crankshaft")
 DEFINE_IMPLICATION(minimal, ignition)
 DEFINE_NEG_IMPLICATION(minimal, crankshaft)
 DEFINE_NEG_IMPLICATION(minimal, use_ic)
 
 // Flags for native WebAssembly.
 DEFINE_BOOL(expose_wasm, true, "expose WASM interface to JavaScript")
 DEFINE_INT(wasm_num_compilation_tasks, 10,
            "number of parallel compilation tasks for wasm")
+DEFINE_INT(wasm_max_mem_pages, 16384, "maximum memory size of a wasm instance")

[titzer, 2017/01/13 14:54:22]

You can actually define this as a uint32_t (which will save you all the casts
elsewhere), but it will parse (in flags.cc) as an int. Since we are already
doing a static_cast<int> there, we might actually already have a bug there if
someone passes a negative number or an out-of-range number. Or you could try to
introduce unsigned types to flags.cc...

[ahaas, 2017/01/17 09:09:55]

I think I did that now, but I'm not sure how flags.cc works in detail.

 DEFINE_BOOL(trace_wasm_encoder, false, "trace encoding of wasm code")
 DEFINE_BOOL(trace_wasm_decoder, false, "trace decoding of wasm code")
 DEFINE_BOOL(trace_wasm_decode_time, false, "trace decoding time of wasm code")
 DEFINE_BOOL(trace_wasm_compiler, false, "trace compiling of wasm code")
 DEFINE_BOOL(trace_wasm_interpreter, false, "trace interpretation of wasm code")
 DEFINE_INT(trace_wasm_ast_start, 0,
            "start function for WASM AST trace (inclusive)")
 DEFINE_INT(trace_wasm_ast_end, 0, "end function for WASM AST trace (exclusive)")
 DEFINE_INT(trace_wasm_text_start, 0,
            "start function for WASM text generation (inclusive)")
@@ skipping 771 matching lines @@
 #undef DEFINE_ALIAS_FLOAT
 #undef DEFINE_ALIAS_ARGS
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META
 #undef FLAG_MODE_DEFINE_IMPLICATIONS
 
 #undef COMMA