mozjs_sys 140.13.0-2

#! /usr/bin/env python3
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

"""This script analyzes a JSON file emitted by DMD."""

import argparse
import collections
import gzip
import io
import json
import os
import platform
import re
import shutil
import sys
import tempfile
from bisect import bisect_right
from functools import cmp_to_key
from typing import Callable

# The DMD output version this script handles.
outputVersion = 5

# If --ignore-alloc-fns is specified, stack frames containing functions that
# match these strings will be removed from the *start* of stack traces. (Once
# we hit a non-matching frame, any subsequent frames won't be removed even if
# they do match.)
allocatorFns = [
    # Matches malloc, replace_malloc, moz_xmalloc, vpx_malloc, js_malloc,
    # pod_malloc, malloc_zone_*, g_malloc.
    "malloc",
    # Matches calloc, replace_calloc, moz_xcalloc, vpx_calloc, js_calloc,
    # pod_calloc, malloc_zone_calloc, pod_callocCanGC.
    "calloc",
    # Matches realloc, replace_realloc, moz_xrealloc, vpx_realloc, js_realloc,
    # pod_realloc, pod_reallocCanGC.
    "realloc",
    # Matches memalign, posix_memalign, replace_memalign, replace_posix_memalign,
    # moz_xmemalign, vpx_memalign, malloc_zone_memalign.
    "memalign",
    "operator new(",
    "operator new[](",
    "g_slice_alloc",
    # This one is necessary to fully filter some sequences of allocation
    # functions that happen in practice. Note that ??? entries that follow
    # non-allocation functions won't be stripped, as explained above.
    "???",
    # Match DMD internals.
    "mozilla::dmd::AllocCallback",
    "mozilla::dmd::StackTrace::Get",
]


def cmp(a, b):
    return (a > b) - (a < b)


class Record:
    """A record is an aggregation of heap blocks that have identical stack
    traces. It can also be used to represent the difference between two
    records."""

    def __init__(self):
        self.numBlocks = 0
        self.reqSize = 0
        self.slopSize = 0
        self.usableSize = 0
        self.allocatedAtDesc = None
        self.reportedAtDescs = []
        self.usableSizes = collections.defaultdict(int)
        self.addrs = []

    def isZero(self, args):
        return (
            self.numBlocks == 0
            and self.reqSize == 0
            and self.slopSize == 0
            and self.usableSize == 0
            and len(self.usableSizes) == 0
        )

    def negate(self):
        self.numBlocks = -self.numBlocks
        self.reqSize = -self.reqSize
        self.slopSize = -self.slopSize
        self.usableSize = -self.usableSize

        negatedUsableSizes = collections.defaultdict(int)
        for usableSize, count in self.usableSizes.items():
            negatedUsableSizes[-usableSize] = count
        self.usableSizes = negatedUsableSizes

    def subtract(self, r):
        # We should only be calling this on records with matching stack traces.
        # Check this.
        assert self.allocatedAtDesc == r.allocatedAtDesc
        assert self.reportedAtDescs == r.reportedAtDescs

        self.numBlocks -= r.numBlocks
        self.reqSize -= r.reqSize
        self.slopSize -= r.slopSize
        self.usableSize -= r.usableSize

        usableSizes1 = self.usableSizes
        usableSizes2 = r.usableSizes
        usableSizes3 = collections.defaultdict(int)
        for usableSize in usableSizes1:
            counts1 = usableSizes1[usableSize]
            if usableSize in usableSizes2:
                counts2 = usableSizes2[usableSize]
                del usableSizes2[usableSize]
                counts3 = counts1 - counts2
                if counts3 != 0:
                    if counts3 < 0:
                        usableSize = -usableSize
                        counts3 = -counts3
                    usableSizes3[usableSize] = counts3
            else:
                usableSizes3[usableSize] = counts1

        for usableSize in usableSizes2:
            usableSizes3[-usableSize] = usableSizes2[usableSize]

        self.usableSizes = usableSizes3

    @staticmethod
    def cmpByUsableSize(r1, r2):
        # Sort by usable size, then by req size.
        return cmp(abs(r1.usableSize), abs(r2.usableSize)) or Record.cmpByReqSize(
            r1, r2
        )

    @staticmethod
    def cmpByReqSize(r1, r2):
        # Sort by req size.
        return cmp(abs(r1.reqSize), abs(r2.reqSize))

    @staticmethod
    def cmpBySlopSize(r1, r2):
        # Sort by slop size.
        return cmp(abs(r1.slopSize), abs(r2.slopSize))

    @staticmethod
    def cmpByNumBlocks(r1, r2):
        # Sort by block counts, then by usable size.
        return cmp(abs(r1.numBlocks), abs(r2.numBlocks)) or Record.cmpByUsableSize(
            r1, r2
        )


sortByChoices = {
    "usable": Record.cmpByUsableSize,  # the default
    "req": Record.cmpByReqSize,
    "slop": Record.cmpBySlopSize,
    "num-blocks": Record.cmpByNumBlocks,
}


def parseCommandLine():
    # 24 is the maximum number of frames that DMD will produce.
    def range_1_24(string):
        value = int(string)
        if value < 1 or value > 24:
            msg = f"{string:s} is not in the range 1..24"
            raise argparse.ArgumentTypeError(msg)
        return value

    description = """
Analyze heap data produced by DMD.
If one file is specified, analyze it; if two files are specified, analyze the
difference.
Input files can be gzipped.
Write to stdout unless -o/--output is specified.
Stack traces are fixed to show function names, filenames and line numbers
unless --no-fix-stacks is specified; stack fixing modifies the original file
and may take some time. If specified, the BREAKPAD_SYMBOLS_PATH environment
variable is used to find breakpad symbols for stack fixing.
"""
    p = argparse.ArgumentParser(description=description)

    p.add_argument(
        "-o",
        "--output",
        type=argparse.FileType("w"),
        help="output file; stdout if unspecified",
    )

    p.add_argument(
        "-f",
        "--max-frames",
        type=range_1_24,
        default=8,
        help="maximum number of frames to consider in each trace",
    )

    p.add_argument(
        "-s",
        "--sort-by",
        choices=sortByChoices.keys(),
        default="usable",
        help="sort the records by a particular metric",
    )

    p.add_argument(
        "-a",
        "--ignore-alloc-fns",
        action="store_true",
        help="ignore allocation functions at the start of traces",
    )

    p.add_argument("--no-fix-stacks", action="store_true", help="do not fix stacks")

    p.add_argument(
        "--clamp-contents",
        action="store_true",
        help="for a scan mode log, clamp addresses to the start of live blocks, "
        "or zero if not in one",
    )

    p.add_argument(
        "--print-clamp-stats",
        action="store_true",
        help="print information about the results of pointer clamping; mostly "
        "useful for debugging clamping",
    )

    p.add_argument(
        "--filter-stacks-for-testing",
        action="store_true",
        help="filter stack traces; only useful for testing purposes",
    )

    p.add_argument(
        "--filter",
        default=[],
        action="append",
        help="Only print entries that have a stack that matches the filter. "
        "A filter may be negated by prefixing it with `!`. "
        "If multiple filters are specified, all of them must match.",
    )

    p.add_argument("input_file", help="a file produced by DMD")

    p.add_argument(
        "input_file2",
        nargs="?",
        help="a file produced by DMD; if present, it is diff'd with input_file",
    )

    return p.parse_args(sys.argv[1:])


# Fix stacks if necessary: first write the output to a tempfile, then replace
# the original file with it.
def fixStackTraces(inputFilename, isZipped, opener):
    # This append() call is needed to make the import statements work when this
    # script is installed as a symlink.
    sys.path.append(os.path.dirname(__file__))

    bpsyms = os.environ.get("BREAKPAD_SYMBOLS_PATH", None)
    sysname = platform.system()
    if bpsyms and os.path.exists(bpsyms):
        import fix_stacks as fixModule

        def fix(line):
            return fixModule.fixSymbols(line, jsonMode=True, breakpadSymsDir=bpsyms)

    elif sysname in ("Linux", "Darwin", "Windows"):
        import fix_stacks as fixModule

        def fix(line):
            return fixModule.fixSymbols(line, jsonMode=True)

    else:
        return

    # Fix stacks, writing output to a temporary file, and then overwrite the
    # original file.
    tmpFile = tempfile.NamedTemporaryFile(delete=False)

    # If the input is gzipped, then the output (written initially to |tmpFile|)
    # should be gzipped as well.
    #
    # And we want to set its pre-gzipped filename to '' rather than the name of
    # the temporary file, so that programs like the Unix 'file' utility don't
    # say that it was called 'tmp6ozTxE' (or something like that) before it was
    # zipped. So that explains the |filename=''| parameter.
    #
    # But setting the filename like that clobbers |tmpFile.name|, so we must
    # get that now in order to move |tmpFile| at the end.
    tmpFilename = tmpFile.name
    if isZipped:
        tmpFile = gzip.GzipFile(filename="", fileobj=tmpFile, mode="wb")

    with opener(inputFilename, "rb") as inputFile:
        for line in inputFile:
            tmpFile.write(fix(line))

    tmpFile.close()

    shutil.move(tmpFilename, inputFilename)


def getDigestFromFile(args, inputFile):
    # Handle gzipped input if necessary.
    isZipped = inputFile.endswith(".gz")
    opener = gzip.open if isZipped else open

    # Fix stack traces unless otherwise instructed.
    if not args.no_fix_stacks:
        fixStackTraces(inputFile, isZipped, opener)

    if args.clamp_contents:
        clampBlockList(args, inputFile, isZipped, opener)

    with opener(inputFile, "rb") as f:
        j = json.load(f)

    if j["version"] != outputVersion:
        raise Exception(f"'version' property isn't '{outputVersion:d}'")

    # Extract the main parts of the JSON object.
    invocation = j["invocation"]
    dmdEnvVar = invocation["dmdEnvVar"]
    mode = invocation["mode"]
    blockList = j["blockList"]
    traceTable = j["traceTable"]
    frameTable = j["frameTable"]

    # Insert the necessary entries for unrecorded stack traces. Note that 'ut'
    # and 'uf' will not overlap with any keys produced by DMD's
    # ToIdStringConverter::Base32() function.
    unrecordedTraceID = "ut"
    unrecordedFrameID = "uf"
    traceTable[unrecordedTraceID] = [unrecordedFrameID]
    frameTable[unrecordedFrameID] = (
        "#00: (no stack trace recorded due to --stacks=partial)"
    )

    # For the purposes of this script, 'scan' behaves like 'live'.
    if mode == "scan":
        mode = "live"

    if mode not in ["live", "dark-matter", "cumulative"]:
        raise Exception(f"bad 'mode' property: '{mode:s}'")

    # Remove allocation functions at the start of traces.
    if args.ignore_alloc_fns:
        # Build a regexp that matches every function in allocatorFns.
        escapedAllocatorFns = map(re.escape, allocatorFns)
        fn_re = re.compile("|".join(escapedAllocatorFns))

        # Remove allocator fns from each stack trace.
        for traceKey, frameKeys in traceTable.items():
            numSkippedFrames = 0
            for frameKey in frameKeys:
                frameDesc = frameTable[frameKey]
                if re.search(fn_re, frameDesc):
                    numSkippedFrames += 1
                else:
                    break
            if numSkippedFrames > 0:
                traceTable[traceKey] = frameKeys[numSkippedFrames:]

    # Trim the number of frames.
    for traceKey, frameKeys in traceTable.items():
        if len(frameKeys) > args.max_frames:
            del frameKeys[args.max_frames :]

    def buildTraceDescription(traceTable, frameTable, traceKey):
        frameKeys = traceTable[traceKey]
        fmt = "    #{:02d}{:}"

        if args.filter_stacks_for_testing:
            # This option is used by `test_dmd.js`, which runs the code in
            # `SmokeDMD.cpp`. When running that test, there is too much
            # variation in the stack traces across different machines and
            # platforms to do exact output matching. However, every stack trace
            # should have at least three frames that contain `DMD` (in one of
            # `DMD.cpp`, `SmokeDMD.cpp`, `SmokeDMD`, or `SmokeDMD.exe`). Some
            # example frames from automation (where `..` indicates excised path
            # segments):
            #
            # Linux debug, with stack fixing using breakpad syms:
            # `#01: replace_realloc(void*, unsigned long) [../dmd/DMD.cpp:1110]`
            #
            # Linux opt, with native stack fixing:
            # `#02: TestFull(char const*, int, char const*, int) (../dmd/test/SmokeDMD.cpp:165)`
            #
            # Mac opt, with native stack fixing:
            # `#03: RunTests() (../build/tests/bin/SmokeDMD + 0x21f9)`
            #
            # Windows opt, with native stack fixing failing due to a missing PDB:
            # `#04: ??? (..\\build\\tests\\bin\\SmokeDMD.exe + 0x1c58)`
            #
            # If we see three such frames, we replace the entire stack trace
            # with a single, predictable frame. This imprecise matching will at
            # least detect if stack fixing fails completely.
            dmd_frame_matches = 0
            for frameKey in frameKeys:
                frameDesc = frameTable[frameKey]
                if "DMD" in frameDesc:
                    dmd_frame_matches += 1
                    if dmd_frame_matches >= 3:
                        return [fmt.format(1, ": ... DMD.cpp ...")]

        # The frame number is always '#00' (see DMD.h for why), so we have to
        # replace that with the correct frame number.
        desc = []
        for n, frameKey in enumerate(traceTable[traceKey], start=1):
            desc.append(fmt.format(n, frameTable[frameKey][3:]))
        return desc

    # Aggregate blocks into records. All sufficiently similar blocks go into a
    # single record.

    if mode in ["live", "cumulative"]:
        liveOrCumulativeRecords = collections.defaultdict(Record)
    elif mode == "dark-matter":
        unreportedRecords = collections.defaultdict(Record)
        onceReportedRecords = collections.defaultdict(Record)
        twiceReportedRecords = collections.defaultdict(Record)

    heapUsableSize = 0
    heapBlocks = 0

    recordKeyPartCache = {}

    for block in blockList:
        # For each block we compute a |recordKey|, and all blocks with the same
        # |recordKey| are aggregated into a single record. The |recordKey| is
        # derived from the block's 'alloc' and 'reps' (if present) stack
        # traces.
        #
        # We use frame descriptions (e.g. "#00: foo (X.cpp:99)") when comparing
        # traces for equality. We can't use trace keys or frame keys because
        # they're not comparable across different DMD runs (which is relevant
        # when doing diffs).
        #
        # Using frame descriptions also fits in with the stack trimming done
        # for --max-frames, which requires that stack traces with common
        # beginnings but different endings to be considered equivalent. E.g. if
        # we have distinct traces T1:[A:D1,B:D2,C:D3] and T2:[X:D1,Y:D2,Z:D4]
        # and we trim the final frame of each they should be considered
        # equivalent because the untrimmed frame descriptions (D1 and D2)
        # match.
        #
        # Having said all that, during a single invocation of dmd.py on a
        # single DMD file, for a single frameKey value the record key will
        # always be the same, and we might encounter it 1000s of times. So we
        # cache prior results for speed.
        def makeRecordKeyPart(traceKey):
            if traceKey in recordKeyPartCache:
                return recordKeyPartCache[traceKey]

            recordKeyPart = str(
                list(map(lambda frameKey: frameTable[frameKey], traceTable[traceKey]))
            )
            recordKeyPartCache[traceKey] = recordKeyPart
            return recordKeyPart

        allocatedAtTraceKey = block.get("alloc", unrecordedTraceID)
        if mode in ["live", "cumulative"]:
            recordKey = makeRecordKeyPart(allocatedAtTraceKey)
            records = liveOrCumulativeRecords
        elif mode == "dark-matter":
            recordKey = makeRecordKeyPart(allocatedAtTraceKey)
            if "reps" in block:
                reportedAtTraceKeys = block["reps"]
                for reportedAtTraceKey in reportedAtTraceKeys:
                    recordKey += makeRecordKeyPart(reportedAtTraceKey)
                if len(reportedAtTraceKeys) == 1:
                    records = onceReportedRecords
                else:
                    records = twiceReportedRecords
            else:
                records = unreportedRecords

        record = records[recordKey]

        if "req" not in block:
            raise Exception("'req' property missing in block'")

        reqSize = block["req"]
        slopSize = block.get("slop", 0)

        if "num" in block:
            num = block["num"]
        else:
            num = 1

        usableSize = reqSize + slopSize
        heapUsableSize += num * usableSize
        heapBlocks += num

        record.numBlocks += num
        record.reqSize += num * reqSize
        record.slopSize += num * slopSize
        record.usableSize += num * usableSize
        if record.allocatedAtDesc is None:
            record.allocatedAtDesc = buildTraceDescription(
                traceTable, frameTable, allocatedAtTraceKey
            )

        # In heap scan mode, we record the address of every block.
        if "addr" in block:
            record.addrs.append(block["addr"])

        if mode in ["live", "cumulative"]:
            pass
        elif mode == "dark-matter":
            if "reps" in block and record.reportedAtDescs == []:

                def f(k):
                    return buildTraceDescription(traceTable, frameTable, k)

                record.reportedAtDescs = list(map(f, reportedAtTraceKeys))
        record.usableSizes[usableSize] += num

    # All the processed data for a single DMD file is called a "digest".
    digest = {}
    digest["dmdEnvVar"] = dmdEnvVar
    digest["mode"] = mode
    digest["heapUsableSize"] = heapUsableSize
    digest["heapBlocks"] = heapBlocks
    if mode in ["live", "cumulative"]:
        digest["liveOrCumulativeRecords"] = liveOrCumulativeRecords
    elif mode == "dark-matter":
        digest["unreportedRecords"] = unreportedRecords
        digest["onceReportedRecords"] = onceReportedRecords
        digest["twiceReportedRecords"] = twiceReportedRecords
    return digest


def diffRecords(args, records1, records2):
    records3 = {}

    # Process records1.
    for k in records1:
        r1 = records1[k]
        if k in records2:
            # This record is present in both records1 and records2.
            r2 = records2[k]
            del records2[k]
            r2.subtract(r1)
            if not r2.isZero(args):
                records3[k] = r2
        else:
            # This record is present only in records1.
            r1.negate()
            records3[k] = r1

    for k in records2:
        # This record is present only in records2.
        records3[k] = records2[k]

    return records3


def diffDigests(args, d1, d2):
    if d1["mode"] != d2["mode"]:
        raise Exception("the input files have different 'mode' properties")

    d3 = {}
    d3["dmdEnvVar"] = (d1["dmdEnvVar"], d2["dmdEnvVar"])
    d3["mode"] = d1["mode"]
    d3["heapUsableSize"] = d2["heapUsableSize"] - d1["heapUsableSize"]
    d3["heapBlocks"] = d2["heapBlocks"] - d1["heapBlocks"]
    if d1["mode"] in ["live", "cumulative"]:
        d3["liveOrCumulativeRecords"] = diffRecords(
            args, d1["liveOrCumulativeRecords"], d2["liveOrCumulativeRecords"]
        )
    elif d1["mode"] == "dark-matter":
        d3["unreportedRecords"] = diffRecords(
            args, d1["unreportedRecords"], d2["unreportedRecords"]
        )
        d3["onceReportedRecords"] = diffRecords(
            args, d1["onceReportedRecords"], d2["onceReportedRecords"]
        )
        d3["twiceReportedRecords"] = diffRecords(
            args, d1["twiceReportedRecords"], d2["twiceReportedRecords"]
        )
    return d3


def printDigest(args, digest):
    dmdEnvVar = digest["dmdEnvVar"]
    mode = digest["mode"]
    heapUsableSize = digest["heapUsableSize"]
    heapBlocks = digest["heapBlocks"]
    if mode in ["live", "cumulative"]:
        liveOrCumulativeRecords = digest["liveOrCumulativeRecords"]
    elif mode == "dark-matter":
        unreportedRecords = digest["unreportedRecords"]
        onceReportedRecords = digest["onceReportedRecords"]
        twiceReportedRecords = digest["twiceReportedRecords"]

    separator = "#" + "-" * 65 + "\n"

    def number(n):
        """Format a number with comma as a separator."""
        return f"{n:,d}"

    def perc(m, n):
        return 0 if n == 0 else (100 * m / n)

    def plural(n):
        return "" if n == 1 else "s"

    # Prints to stdout, or to file if -o/--output was specified.
    def out(*arguments, **kwargs):
        print(*arguments, file=args.output, **kwargs)

    def printStack(traceDesc):
        for frameDesc in traceDesc:
            out(frameDesc)

    def printRecords(recordKind, records, heapUsableSize):
        RecordKind = recordKind.capitalize()
        out(separator)
        numRecords = len(records)
        cmpRecords = sortByChoices[args.sort_by]
        sortedRecords = sorted(
            records.values(), key=cmp_to_key(cmpRecords), reverse=True
        )
        kindBlocks = 0
        kindUsableSize = 0
        maxRecord = 1000

        def is_match(rec: Record, key: str):
            return any(key in desc for desc in rec.allocatedAtDesc)

        for arg in args.filter:
            key: str
            cond: Callable[[Record], bool]
            if arg.startswith("\\"):
                # just in case you really need to start a filter with '!' (or '\')
                key = arg[1:]
                cond = is_match
            elif arg.startswith("!"):
                key = arg[1:]

                def cond(rec, key):
                    return not is_match(rec, key)  # noqa: E731

            else:
                key = arg
                cond = is_match
            sortedRecords = [rec for rec in sortedRecords if cond(rec, key)]

        # First iteration: get totals, etc.
        for record in sortedRecords:
            kindBlocks += record.numBlocks
            kindUsableSize += record.usableSize

        # Second iteration: print.
        if numRecords == 0:
            out(f"# no {recordKind} heap blocks\n")

        kindCumulativeUsableSize = 0
        for i, record in enumerate(sortedRecords, start=1):
            # Stop printing at the |maxRecord|th record.
            if i == maxRecord:
                out(f"# {RecordKind}: stopping after {i:,d} heap block records\n")
                break

            kindCumulativeUsableSize += record.usableSize

            out(RecordKind + " {")
            out(
                f"  {number(record.numBlocks)} block{plural(record.numBlocks)} in heap block record {i:,d} of {numRecords:,d}"
            )
            if record.addrs:
                if args.filter_stacks_for_testing:
                    # These addresses will vary, so for testing replace them with a fixed value.
                    baseAddrs = ["dadadada" for a in record.addrs]
                else:
                    baseAddrs = sorted(record.addrs)
                addrsString = ", ".join([f"0x{a}" for a in baseAddrs])
                out("  block addresses: " + addrsString)
            out(
                f"  {number(record.usableSize)} bytes ({number(record.reqSize)} requested / {number(record.slopSize)} slop)"
            )

            usableSizes = sorted(
                record.usableSizes.items(), key=lambda x: abs(x[0]), reverse=True
            )
            hasSingleBlock = len(usableSizes) == 1 and usableSizes[0][1] == 1

            if not hasSingleBlock:
                out("  Individual block sizes: ", end="")
                if len(usableSizes) == 0:
                    out("(no change)", end="")
                else:
                    isFirst = True
                    for usableSize, count in usableSizes:
                        if not isFirst:
                            out("; ", end="")
                        out(f"{number(usableSize)}", end="")
                        if count > 1:
                            out(f" x {count:,d}", end="")
                        isFirst = False
                out()

            out(
                f"  {perc(record.usableSize, heapUsableSize):4.2f}% of the heap ({perc(kindCumulativeUsableSize, heapUsableSize):4.2f}% cumulative)"
            )
            if mode in ["live", "cumulative"]:
                pass
            elif mode == "dark-matter":
                out(
                    f"  {perc(record.usableSize, kindUsableSize):4.2f}% of {recordKind} ({perc(kindCumulativeUsableSize, kindUsableSize):4.2f}% cumulative)"
                )
            out("  Allocated at {")
            printStack(record.allocatedAtDesc)
            out("  }")
            if mode in ["live", "cumulative"]:
                pass
            elif mode == "dark-matter":
                for n, reportedAtDesc in enumerate(record.reportedAtDescs):
                    again = "again " if n > 0 else ""
                    out(f"  Reported {again}at {{")
                    printStack(reportedAtDesc)
                    out("  }")
            out("}\n")

        return (kindUsableSize, kindBlocks)

    def printInvocation(n, dmdEnvVar, mode):
        out(f"Invocation{n} {{")
        if dmdEnvVar is None:
            out("  $DMD is undefined")
        else:
            out("  $DMD = '" + dmdEnvVar + "'")
        out("  Mode = '" + mode + "'")
        out("}\n")

    # Print command line. Strip dirs so the output is deterministic, which is
    # needed for testing.
    out(separator, end="")
    out("# " + " ".join(map(os.path.basename, sys.argv)) + "\n")

    # Print invocation(s).
    if type(dmdEnvVar) is not tuple:
        printInvocation("", dmdEnvVar, mode)
    else:
        printInvocation(" 1", dmdEnvVar[0], mode)
        printInvocation(" 2", dmdEnvVar[1], mode)

    # Print records.
    if mode in ["live", "cumulative"]:
        liveOrCumulativeUsableSize, liveOrCumulativeBlocks = printRecords(
            mode, liveOrCumulativeRecords, heapUsableSize
        )
    elif mode == "dark-matter":
        twiceReportedUsableSize, twiceReportedBlocks = printRecords(
            "twice-reported", twiceReportedRecords, heapUsableSize
        )

        unreportedUsableSize, unreportedBlocks = printRecords(
            "unreported", unreportedRecords, heapUsableSize
        )

        onceReportedUsableSize, onceReportedBlocks = printRecords(
            "once-reported", onceReportedRecords, heapUsableSize
        )

    # Print summary.
    out(separator)
    out("Summary {")
    if mode in ["live", "cumulative"]:
        out(
            f"  Total: {number(liveOrCumulativeUsableSize)} bytes in {number(liveOrCumulativeBlocks)} blocks"
        )
    elif mode == "dark-matter":
        fmt = "  {:15} {:>12} bytes ({:6.2f}%) in {:>7} blocks ({:6.2f}%)"
        out(fmt.format("Total:", number(heapUsableSize), 100, number(heapBlocks), 100))
        out(
            fmt.format(
                "Unreported:",
                number(unreportedUsableSize),
                perc(unreportedUsableSize, heapUsableSize),
                number(unreportedBlocks),
                perc(unreportedBlocks, heapBlocks),
            )
        )
        out(
            fmt.format(
                "Once-reported:",
                number(onceReportedUsableSize),
                perc(onceReportedUsableSize, heapUsableSize),
                number(onceReportedBlocks),
                perc(onceReportedBlocks, heapBlocks),
            )
        )
        out(
            fmt.format(
                "Twice-reported:",
                number(twiceReportedUsableSize),
                perc(twiceReportedUsableSize, heapUsableSize),
                number(twiceReportedBlocks),
                perc(twiceReportedBlocks, heapBlocks),
            )
        )
    out("}\n")


#############################
# Pretty printer for DMD JSON
#############################


def prettyPrintDmdJson(out, j):
    out.write("{\n")

    out.write(' "version": {0},\n'.format(j["version"]))
    out.write(' "invocation": ')
    json.dump(j["invocation"], out, sort_keys=True)
    out.write(",\n")

    out.write(' "blockList": [')
    first = True
    for b in j["blockList"]:
        out.write("" if first else ",")
        out.write("\n  ")
        json.dump(b, out, sort_keys=True)
        first = False
    out.write("\n ],\n")

    out.write(' "traceTable": {')
    first = True
    for k, l in j["traceTable"].items():
        out.write("" if first else ",")
        out.write(f'\n  "{k}": {json.dumps(l)}')
        first = False
    out.write("\n },\n")

    out.write(' "frameTable": {')
    first = True
    for k, v in j["frameTable"].items():
        out.write("" if first else ",")
        out.write(f'\n  "{k}": {json.dumps(v)}')
        first = False
    out.write("\n }\n")

    out.write("}\n")


##################################################################
# Code for clamping addresses using conservative pointer analysis.
##################################################################


# Start is the address of the first byte of the block, while end is
# the address of the first byte after the final byte in the block.
class AddrRange:
    def __init__(self, block, length):
        self.block = block
        self.start = int(block, 16)
        self.length = length
        self.end = self.start + self.length

        assert self.start > 0
        assert length >= 0


class ClampStats:
    def __init__(self):
        # Number of pointers already pointing to the start of a block.
        self.startBlockPtr = 0

        # Number of pointers pointing to the middle of a block. These
        # are clamped to the start of the block they point into.
        self.midBlockPtr = 0

        # Number of null pointers.
        self.nullPtr = 0

        # Number of non-null pointers that didn't point into the middle
        # of any blocks. These are clamped to null.
        self.nonNullNonBlockPtr = 0

    def clampedBlockAddr(self, sameAddress):
        if sameAddress:
            self.startBlockPtr += 1
        else:
            self.midBlockPtr += 1

    def nullAddr(self):
        self.nullPtr += 1

    def clampedNonBlockAddr(self):
        self.nonNullNonBlockPtr += 1

    def log(self):
        sys.stderr.write("Results:\n")
        sys.stderr.write(
            "  Number of pointers already pointing to start of blocks: "
            + str(self.startBlockPtr)
            + "\n"
        )
        sys.stderr.write(
            "  Number of pointers clamped to start of blocks: "
            + str(self.midBlockPtr)
            + "\n"
        )
        sys.stderr.write(
            "  Number of non-null pointers not pointing into blocks "
            "clamped to null: " + str(self.nonNullNonBlockPtr) + "\n"
        )
        sys.stderr.write("  Number of null pointers: " + str(self.nullPtr) + "\n")


# Search the block ranges array for a block that address points into.
# The search is carried out in an array of starting addresses for each blocks
# because it is faster.
def clampAddress(blockRanges, blockStarts, clampStats, address):
    i = bisect_right(blockStarts, address)

    # Any addresses completely out of the range should have been eliminated already.
    assert i > 0
    r = blockRanges[i - 1]
    assert r.start <= address

    if address >= r.end:
        assert address < blockRanges[i].start
        clampStats.clampedNonBlockAddr()
        return "0"

    clampStats.clampedBlockAddr(r.start == address)
    return r.block


def clampBlockList(args, inputFileName, isZipped, opener):
    # XXX This isn't very efficient because we end up reading and writing
    # the file multiple times.
    with opener(inputFileName, "rb") as f:
        j = json.load(f)

    if j["version"] != outputVersion:
        raise Exception(f"'version' property isn't '{outputVersion:d}'")

    # Check that the invocation is reasonable for contents clamping.
    invocation = j["invocation"]
    if invocation["mode"] != "scan":
        raise Exception("Log was taken in mode " + invocation["mode"] + " not scan")

    sys.stderr.write("Creating block range list.\n")
    blockList = j["blockList"]
    blockRanges = []
    for block in blockList:
        blockRanges.append(AddrRange(block["addr"], block["req"]))
    blockRanges.sort(key=lambda r: r.start)

    # Make sure there are no overlapping blocks.
    prevRange = blockRanges[0]
    for currRange in blockRanges[1:]:
        assert prevRange.end <= currRange.start
        prevRange = currRange

    sys.stderr.write("Clamping block contents.\n")
    clampStats = ClampStats()
    firstAddr = blockRanges[0].start
    lastAddr = blockRanges[-1].end

    blockStarts = []
    for r in blockRanges:
        blockStarts.append(r.start)

    for block in blockList:
        # Small blocks don't have any contents.
        if "contents" not in block:
            continue

        cont = block["contents"]
        for i in range(len(cont)):
            address = int(cont[i], 16)

            if address == 0:
                clampStats.nullAddr()
                continue

            # If the address is before the first block or after the last
            # block then it can't be within a block.
            if address < firstAddr or address >= lastAddr:
                clampStats.clampedNonBlockAddr()
                cont[i] = "0"
                continue

            cont[i] = clampAddress(blockRanges, blockStarts, clampStats, address)

        # Remove any trailing nulls.
        while len(cont) and cont[-1] == "0":
            cont.pop()

    if args.print_clamp_stats:
        clampStats.log()

    sys.stderr.write("Saving file.\n")
    tmpFile = tempfile.NamedTemporaryFile(delete=False)
    tmpFilename = tmpFile.name
    if isZipped:
        tmpFile = gzip.GzipFile(filename="", fileobj=tmpFile, mode="wb")
    prettyPrintDmdJson(io.TextIOWrapper(tmpFile, encoding="utf-8"), j)
    tmpFile.close()
    shutil.move(tmpFilename, inputFileName)


def main():
    args = parseCommandLine()
    digest = getDigestFromFile(args, args.input_file)
    if args.input_file2:
        digest2 = getDigestFromFile(args, args.input_file2)
        digest = diffDigests(args, digest, digest2)
    printDigest(args, digest)


if __name__ == "__main__":
    main()