Introduce sanstats tool and llvm::CreateSanitizerStatReport function.

[pcc]

Summary

This is part of a new statistics gathering feature for the sanitizers.
See clang/docs/SanitizerStats.rst for further info and docs.

[krasin1]

lib/Transforms/Utils/SanitizerStats.cpp

54

Is that a correct error handling for the unknown format? Should we warn the user? May be even fail hard?

tools/sanstats/sanstats.cpp

42

This expression is hard to read. For example, I had to think thrice, if it increments Begin or the value that Begin points to.

Please, split it into a few lines, like:

while (Begin < End && Pos != Size) {

Result |= uint64_t(uint8_t(*Begin)) << (Pos * 8);
Begin++;
Pos++;

}

Also, if that's a hot function, I would recommend to consider a faster implementation that will read the required number of bytes at once, and then swap the bytes with one of the standard helper functions. If this function is rarely called, feel free to leave it as is (modulo my comment above)

48

isn't a reimplementation of strnlen?

66

At this point Begin could be greater than End. May be check in the previous line?
Alternatively, make ReadLE to accept a pointer to Begin and let it to update it.

127

I highly suggest to check Begin < End and optionally check that Begin == End after the loop.

Otherwise, it's not hard to imaging that a tiny mistake somewhere would just Begin slightly past End and then we'll have to read after the end of the buffer until SEGFAULT stops this heroic attempt to overflow uintptr.

[pcc]

• Address review comments

lib/Transforms/Utils/SanitizerStats.cpp

54

It would probably be appropriate to call report_fatal_error here.

tools/sanstats/sanstats.cpp

48

Yes, but strnlen is not part of the C standard, and I think it's clearer to be explicit.

66

At this point Begin could be greater than End. May be check in the previous line?

We defend against this in ReadLE.

Alternatively, make ReadLE to accept a pointer to Begin and let it to update it.

I considered this, but it's harder to distinguish between short reads and EOF this way.

127

I added an assertion that should catch this.

[krasin]

LGTM

[pcc]

• Switch to an alternative in-memory representation that avoids the need for linker magic

include/llvm/Transforms/Utils/SanitizerStats.h

+//===- SanitizerStats.h - Sanitizer statistics gathering  -------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Declares functions and data structures for sanitizer statistics gathering.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_UTILS_SANITIZERSTATS_H
+#define LLVM_TRANSFORMS_UTILS_SANITIZERSTATS_H
+
+#include "llvm/IR/IRBuilder.h"
+
+namespace llvm {
+
+// Number of bits in data that are used for the sanitizer kind. Needs to match
+// __sanitizer::kKindBits in compiler-rt/lib/stats/stats.h
+enum { kSanitizerStatKindBits = 3 };
+
+enum SanitizerStatKind {
+  SanStat_CFI_VCall,
+  SanStat_CFI_NVCall,
+  SanStat_CFI_DerivedCast,
+  SanStat_CFI_UnrelatedCast,
+  SanStat_CFI_ICall,
+};
+
+/// Generates code into B that increments a location-specific counter tagged
+/// with the given sanitizer kind SK.
+void CreateSanitizerStatReport(IRBuilder<> &B, SanitizerStatKind SK);
+
+}
+
+#endif

lib/Transforms/Utils/CMakeLists.txt

add_llvm_library(LLVMTransformUtils
   LoopVersioning.cpp
   LowerInvoke.cpp
   LowerSwitch.cpp
   Mem2Reg.cpp
   MetaRenamer.cpp
   ModuleUtils.cpp
   PromoteMemoryToRegister.cpp
   SSAUpdater.cpp
+  SanitizerStats.cpp
   SimplifyCFG.cpp
   SimplifyIndVar.cpp
   SimplifyInstructions.cpp
   SimplifyLibCalls.cpp
   SplitModule.cpp
   SymbolRewriter.cpp
   UnifyFunctionExitNodes.cpp
   Utils.cpp
   ValueMapper.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Transforms
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Transforms/Utils
   )
 
 add_dependencies(LLVMTransformUtils intrinsics_gen)

lib/Transforms/Utils/SanitizerStats.cpp

+//===- SanitizerStats.cpp - Sanitizer statistics gathering ----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Implements code generation for sanitizer statistics gathering.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/SanitizerStats.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Module.h"
+
+using namespace llvm;
+
+void llvm::CreateSanitizerStatReport(IRBuilder<> &B, SanitizerStatKind SK) {
+  Function *F = B.GetInsertBlock()->getParent();
+  Module *M = F->getParent();
+  PointerType *Int8PtrTy = B.getInt8PtrTy();
+  IntegerType *IntPtrTy = B.getIntPtrTy(M->getDataLayout());
+  ArrayType *StatsTy = ArrayType::get(Int8PtrTy, 2);
+
+  auto GV = new GlobalVariable(
+      *M, StatsTy, false, GlobalValue::PrivateLinkage,
+      ConstantArray::get(
+          StatsTy, {Constant::getNullValue(Int8PtrTy),
+                    ConstantExpr::getIntToPtr(
+                        ConstantInt::get(
+                            IntPtrTy, uint64_t(SK) << (IntPtrTy->getBitWidth() -
+                                                       kSanitizerStatKindBits)),
+                        Int8PtrTy)}));
+  GV->setComdat(F->getComdat());
+  // See compiler-rt/lib/stats/stats_client.cc for the rationale behind each
+  // section name.
+  switch (Triple(M->getTargetTriple()).getObjectFormat()) {
+  case Triple::COFF:
+    GV->setSection("san_stat$u");
+    break;
+  case Triple::ELF:
+    GV->setSection("san_stat");
+    break;
+  case Triple::MachO:
+    GV->setSection("__DATA,san_stat");
+    break;
+  case Triple::UnknownObjectFormat:
+    break;
+  }
+
+  FunctionType *StatReportTy =
+      FunctionType::get(B.getVoidTy(), Int8PtrTy, false);
+  Constant *StatReport = M->getOrInsertFunction(
+      "__sanitizer_stat_report", StatReportTy);
+
+  B.CreateCall(StatReport, ConstantExpr::getBitCast(GV, Int8PtrTy));
+}

test/CMakeLists.txt

set(LLVM_TEST_DEPENDS
           llvm-size
           llvm-split
           llvm-symbolizer
           llvm-tblgen
           not
           obj2yaml
           opt
           sancov
+          sanstats
           verify-uselistorder
           yaml-bench
           yaml2obj
         )
 
 # If Intel JIT events are supported, depend on a tool that tests the listener.
 if( LLVM_USE_INTEL_JITEVENTS )
   set(LLVM_TEST_DEPENDS ${LLVM_TEST_DEPENDS} llvm-jitlistener)

test/lit.cfg

for pattern in [r"\bbugpoint\b(?!-)",
                 r"\bllvm-split\b",
                 r"\bllvm-tblgen\b",
                 r"\bllvm-c-test\b",
                 NOJUNK + r"\bllvm-symbolizer\b",
                 NOJUNK + r"\bopt\b",
                 r"\bFileCheck\b",
                 r"\bobj2yaml\b",
                 NOJUNK + r"\bsancov\b",
+                NOJUNK + r"\bsanstats\b",
                 r"\byaml2obj\b",
                 r"\byaml-bench\b",
                 r"\bverify-uselistorder\b",
                 # Handle these specially as they are strings searched
                 # for during testing.
                 r"\| \bcount\b",
                 r"\| \bnot\b"]:
     tool_name, tool_path, tool_pipe = find_tool_substitution(pattern)

test/tools/sanstats/elf.test

+# RUN: yaml2obj -format=elf %s > %t1.o
+# RUN: yaml2obj -format=elf %s > %t2.o
+
+# RUN: echo -ne "\x04" > %t.stats
+
+# RUN: echo -ne "%t1.o\x00" >> %t.stats
+# RUN: echo -ne "\x01\x00\x00\x00\x01\x00\x00\x00" >> %t.stats
+# RUN: echo -ne "\x11\x00\x00\x00\x02\x00\x00\x20" >> %t.stats
+# RUN: echo -ne "\x21\x00\x00\x00\x03\x00\x00\x40" >> %t.stats
+# RUN: echo -ne "\x01\x00\x00\x00\x04\x00\x00\x60" >> %t.stats
+# RUN: echo -ne "\x11\x00\x00\x00\x05\x00\x00\x80" >> %t.stats
+# RUN: echo -ne "\x21\x00\x00\x00\x06\x00\x00\xa0" >> %t.stats
+# RUN: echo -ne "\x00\x00\x00\x00\x00\x00\x00\x00" >> %t.stats
+
+# RUN: echo -ne "%t2.o\x00" >> %t.stats
+# RUN: echo -ne "\x21\x00\x00\x00\x07\x00\x00\x00" >> %t.stats
+# RUN: echo -ne "\x11\x00\x00\x00\x08\x00\x00\x20" >> %t.stats
+# RUN: echo -ne "\x01\x00\x00\x00\x09\x00\x00\x40" >> %t.stats
+# RUN: echo -ne "\x21\x00\x00\x00\x0a\x00\x00\x60" >> %t.stats
+# RUN: echo -ne "\x11\x00\x00\x00\x0b\x00\x00\x80" >> %t.stats
+# RUN: echo -ne "\x01\x00\x00\x00\x0c\x00\x00\xa0" >> %t.stats
+# RUN: echo -ne "\x00\x00\x00\x00\x00\x00\x00\x00" >> %t.stats
+
+# RUN: sanstats %t.stats | FileCheck %s
+
+# CHECK: /tmp/f.c:1 f1 cfi-vcall 1
+# CHECK: /tmp/f.c:2 f2 cfi-nvcall 2
+# CHECK: /tmp/f.c:3 f3 cfi-derived-cast 3
+# CHECK: /tmp/f.c:1 f1 cfi-unrelated-cast 4
+# CHECK: /tmp/f.c:2 f2 cfi-icall 5
+# CHECK: /tmp/f.c:3 f3 <unknown> 6
+
+# CHECK: /tmp/f.c:3 f3 cfi-vcall 7
+# CHECK: /tmp/f.c:2 f2 cfi-nvcall 8
+# CHECK: /tmp/f.c:1 f1 cfi-derived-cast 9
+# CHECK: /tmp/f.c:3 f3 cfi-unrelated-cast 10
+# CHECK: /tmp/f.c:2 f2 cfi-icall 11
+# CHECK: /tmp/f.c:1 f1 <unknown> 12
+
+---
+FileHeader:      
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:        
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x0000000000000010
+    Content:         554889E55DC3662E0F1F840000000000554889E55DC3662E0F1F840000000000554889E55DC3
+  - Name:            .debug_str
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_MERGE, SHF_STRINGS ]
+    AddressAlign:    0x0000000000000001
+    Content:         636C616E672076657273696F6E20332E382E3020287472756E6B203235353339332920286C6C766D2F7472756E6B203235353734352900662E63002F746D7000663100663200663300
+  - Name:            .debug_loc
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         ''
+  - Name:            .debug_abbrev
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         011101250E1305030E10171B0E110112060000022E00110112064018030E3A0B3B0B3F19000000
+  - Name:            .debug_info
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         660000000400000000000801000000000C0000000000000000000000000000000000000000002600000002000000000000000006000000015600000000010102000000000000000006000000015600000000010202000000000000000006000000015600000000010300
+  - Name:            .rela.debug_info
+    Type:            SHT_RELA
+    Link:            .symtab
+    AddressAlign:    0x0000000000000008
+    Info:            .debug_info
+    Relocations:     
+      - Offset:          0x0000000000000006
+        Symbol:          ''
+        Type:            R_X86_64_32
+      - Offset:          0x000000000000000C
+        Symbol:          ''
+        Type:            R_X86_64_32
+      - Offset:          0x0000000000000012
+        Symbol:          ''
+        Type:            R_X86_64_32
+        Addend:          55
+      - Offset:          0x0000000000000016
+        Symbol:          ''
+        Type:            R_X86_64_32
+      - Offset:          0x000000000000001A
+        Symbol:          ''
+        Type:            R_X86_64_32
+        Addend:          59
+      - Offset:          0x000000000000001E
+        Symbol:          ''
+        Type:            R_X86_64_64
+      - Offset:          0x000000000000002B
+        Symbol:          ''
+        Type:            R_X86_64_64
+      - Offset:          0x0000000000000039
+        Symbol:          ''
+        Type:            R_X86_64_32
+        Addend:          64
+      - Offset:          0x0000000000000040
+        Symbol:          ''
+        Type:            R_X86_64_64
+        Addend:          16
+      - Offset:          0x000000000000004E
+        Symbol:          ''
+        Type:            R_X86_64_32
+        Addend:          67
+      - Offset:          0x0000000000000055
+        Symbol:          ''
+        Type:            R_X86_64_64
+        Addend:          32
+      - Offset:          0x0000000000000063
+        Symbol:          ''
+        Type:            R_X86_64_32
+        Addend:          70
+  - Name:            .debug_ranges
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         ''
+  - Name:            .debug_pubnames
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         230000000200000000006A0000002A0000006631003F0000006632005400000066330000000000
+  - Name:            .rela.debug_pubnames
+    Type:            SHT_RELA
+    Link:            .symtab
+    AddressAlign:    0x0000000000000008
+    Info:            .debug_pubnames
+    Relocations:     
+      - Offset:          0x0000000000000006
+        Symbol:          ''
+        Type:            R_X86_64_32
+  - Name:            .comment
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_MERGE, SHF_STRINGS ]
+    AddressAlign:    0x0000000000000001
+    Content:         00636C616E672076657273696F6E20332E382E3020287472756E6B203235353339332920286C6C766D2F7472756E6B203235353734352900
+  - Name:            .note.GNU-stack
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         ''
+  - Name:            .eh_frame
+    Type:            SHT_X86_64_UNWIND
+    Flags:           [ SHF_ALLOC ]
+    AddressAlign:    0x0000000000000008
+    Content:         1400000000000000017A5200017810011B0C070890010000180000001C000000000000000600000000410E108602430D060000001800000038000000000000000600000000410E108602430D060000001C00000054000000000000000600000000410E108602430D0600000000000000
+  - Name:            .rela.eh_frame
+    Type:            SHT_RELA
+    Link:            .symtab
+    AddressAlign:    0x0000000000000008
+    Info:            .eh_frame
+    Relocations:     
+      - Offset:          0x0000000000000020
+        Symbol:          ''
+        Type:            R_X86_64_PC32
+      - Offset:          0x000000000000003C
+        Symbol:          ''
+        Type:            R_X86_64_PC32
+        Addend:          16
+      - Offset:          0x0000000000000058
+        Symbol:          ''
+        Type:            R_X86_64_PC32
+        Addend:          32
+  - Name:            .debug_line
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000001
+    Content:         4300000002001A0000000101FB0E0D00010101010000000100000100662E630000000000000902000000000000000001050C0A4A0500BB050C0A4A0500BB050C0A4A0202000101
+  - Name:            .rela.debug_line
+    Type:            SHT_RELA
+    Link:            .symtab
+    AddressAlign:    0x0000000000000008
+    Info:            .debug_line
+    Relocations:     
+      - Offset:          0x0000000000000027
+        Symbol:          ''
+        Type:            R_X86_64_64
+Symbols:         
+  Local:           
+    - Name:            f.c
+      Type:            STT_FILE
+    - Type:            STT_SECTION
+      Section:         .text
+    - Type:            STT_SECTION
+      Section:         .debug_str
+    - Type:            STT_SECTION
+      Section:         .debug_abbrev
+    - Type:            STT_SECTION
+      Section:         .debug_info
+    - Type:            STT_SECTION
+      Section:         .debug_line
+  Global:          
+    - Name:            f1
+      Type:            STT_FUNC
+      Section:         .text
+      Size:            0x0000000000000006
+    - Name:            f2
+      Type:            STT_FUNC
+      Section:         .text
+      Value:           0x0000000000000010
+      Size:            0x0000000000000006
+    - Name:            f3
+      Type:            STT_FUNC
+      Section:         .text
+      Value:           0x0000000000000020
+      Size:            0x0000000000000006
+...

tools/Makefile

 # in parallel builds.  Please retain this ordering.
 DIRS := llvm-config
 PARALLEL_DIRS := opt llvm-as llvm-dis llc llvm-ar llvm-nm llvm-link \
                  lli llvm-extract llvm-mc bugpoint llvm-bcanalyzer llvm-diff \
                  llvm-objdump llvm-readobj llvm-rtdyld \
                  llvm-dwarfdump llvm-cov llvm-size llvm-stress llvm-mcmarkup \
                  llvm-profdata llvm-symbolizer obj2yaml yaml2obj llvm-c-test \
                  llvm-cxxdump verify-uselistorder dsymutil llvm-pdbdump \
-                 llvm-split sancov llvm-dwp
+                 llvm-split sancov sanstats llvm-dwp
 
 # If Intel JIT Events support is configured, build an extra tool to test it.
 ifeq ($(USE_INTEL_JITEVENTS), 1)
   PARALLEL_DIRS += llvm-jitlistener
 endif
 
 # Let users override the set of tools to build from the command line.
 ifdef ONLY_TOOLS

tools/sanstats/CMakeLists.txt

+set(LLVM_LINK_COMPONENTS
+  Support
+  Symbolize
+  )
+
+add_llvm_tool(sanstats
+  sanstats.cpp
+  )

tools/sanstats/Makefile

+##===- tools/sanstats/Makefile -----------------------------*- Makefile -*-===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+##===----------------------------------------------------------------------===##
+
+LEVEL := ../..
+TOOLNAME := sanstats
+LINK_COMPONENTS := Support Symbolize
+
+# This tool has no plugins, optimize startup time.
+TOOL_NO_EXPORTS := 1
+
+include $(LEVEL)/Makefile.common

tools/sanstats/sanstats.cpp

+//===- sanstats.cpp - Sanitizer statistics dumper -------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This tool dumps statistics information from files in the format produced
+// by clang's -fsanitize-stats feature.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DebugInfo/Symbolize/Symbolize.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/ErrorOr.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Transforms/Utils/SanitizerStats.h"
+#include <stdint.h>
+
+using namespace llvm;
+
+static cl::opt<std::string> ClInputFile(cl::Positional, cl::Required,
+                                        cl::desc("<filename>"));
+
+static cl::opt<bool> ClDemangle("demangle", cl::init(false),
+                                cl::desc("Print demangled function name."));
+
+inline uint64_t KindFromData(uint64_t Data, char SizeofPtr) {
+  return Data >> (SizeofPtr * 8 - kSanitizerStatKindBits);
+}
+
+inline uint64_t CountFromData(uint64_t Data, char SizeofPtr) {
+  return Data & ((1ull << (SizeofPtr * 8 - kSanitizerStatKindBits)) - 1);
+}
+
+uint64_t ReadLE(char Size, const char *Begin, const char *End) {
+  uint64_t Result = 0;
+  char Pos = 0;
+  while (Begin < End && Pos != Size)
+    Result |= uint64_t(uint8_t(*Begin++)) << (Pos++ * 8);
+  return Result;
+}
+
+const char *ReadModule(char SizeofPtr, const char *Begin, const char *End) {
+  const char *FilenameBegin = Begin;
+  while (Begin != End && *Begin)
+    ++Begin;
+  if (Begin == End)
+    return 0;
+  StringRef Filename(FilenameBegin, Begin - FilenameBegin);
+
+  ++Begin;
+  if (Begin == End)
+    return 0;
+
+  symbolize::LLVMSymbolizer::Options SymbolizerOptions;
+  SymbolizerOptions.Demangle = ClDemangle;
+  SymbolizerOptions.UseSymbolTable = true;
+  symbolize::LLVMSymbolizer Symbolizer(SymbolizerOptions);
+
+  while (1) {
+    uint64_t Addr = ReadLE(SizeofPtr, Begin, End);
+    Begin += SizeofPtr;
+    uint64_t Data = ReadLE(SizeofPtr, Begin, End);
+    Begin += SizeofPtr;
+
+    if (Begin > End)
+      return 0;
+    if (Addr == 0 && Data == 0)
+      return Begin;
+    if (Begin == End)
+      return 0;
+
+    ErrorOr<DILineInfo> LineInfo = Symbolizer.symbolizeCode(Filename, Addr);
+    if (LineInfo) {
+      llvm::outs() << LineInfo->FileName << ':' << LineInfo->Line << ' '
+                   << LineInfo->FunctionName << ' ';
+    } else {
+      llvm::outs() << "<error> ";
+    }
+
+    switch (KindFromData(Data, SizeofPtr)) {
+    case SanStat_CFI_VCall:
+      llvm::outs() << "cfi-vcall";
+      break;
+    case SanStat_CFI_NVCall:
+      llvm::outs() << "cfi-nvcall";
+      break;
+    case SanStat_CFI_DerivedCast:
+      llvm::outs() << "cfi-derived-cast";
+      break;
+    case SanStat_CFI_UnrelatedCast:
+      llvm::outs() << "cfi-unrelated-cast";
+      break;
+    case SanStat_CFI_ICall:
+      llvm::outs() << "cfi-icall";
+      break;
+    default:
+      llvm::outs() << "<unknown>";
+      break;
+    }
+
+    llvm::outs() << " " << CountFromData(Data, SizeofPtr) << '\n';
+  }
+}
+
+int main(int argc, char **argv) {
+  cl::ParseCommandLineOptions(argc, argv,
+                              "Sanitizer Statistics Processing Tool");
+
+  ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
+      MemoryBuffer::getFile(ClInputFile, -1, false);
+  if (!MBOrErr) {
+    errs() << argv[0] << ": " << ClInputFile << ": "
+           << MBOrErr.getError().message() << '\n';
+    return 1;
+  }
+  std::unique_ptr<MemoryBuffer> MB = std::move(MBOrErr.get());
+  const char *Begin = MB->getBufferStart(), *End = MB->getBufferEnd();
+  if (Begin == End) {
+    errs() << argv[0] << ": " << ClInputFile << ": short read\n";
+    return 1;
+  }
+  char SizeofPtr = *Begin++;
+  while (Begin != End) {
+    Begin = ReadModule(SizeofPtr, Begin, End);
+    if (Begin == 0) {
+      errs() << argv[0] << ": " << ClInputFile << ": short read\n";
+      return 1;
+    }
+  }
+}