Introduce a string_ostream string builder facilty

string_ostream is a safe and efficient string builder that combines opaque
stack storage with a built-in ostream interface.

small_string_ostream<bytes> additionally permits an explicit stack storage size
other than the default 128 bytes to be provided. Beyond that, storage is
transferred to the heap.

This convenient class can be used in most places an
std::string+raw_string_ostream pair or SmallString<>+raw_svector_ostream pair
would previously have been used, in order to guarantee consistent access
without byte truncation.

The patch also converts much of LLVM to use the new facility. These changes
include several probable bug fixes for truncated output, a programming error
that's no longer possible with the new interface.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211749 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 16 insertions, 25 deletions

diff --git a/lib/MC/MCAsmStreamer.cpp b/lib/MC/MCAsmStreamer.cpp
index da235ec1d3..a3a81a6bc7 100644
--- a/lib/MC/MCAsmStreamer.cpp
+++ b/lib/MC/MCAsmStreamer.cpp
@@ -1175,9 +1175,10 @@ void MCAsmStreamer::AddEncodingComment(const MCInst &Inst,
   raw_ostream &OS = GetCommentOS();
   SmallString<256> Code;
   SmallVector<MCFixup, 4> Fixups;
-  raw_svector_ostream VecOS(Code);
-  Emitter->EncodeInstruction(Inst, VecOS, Fixups, STI);
-  VecOS.flush();
+  {
+    raw_svector_ostream VecOS(Code);
+    Emitter->EncodeInstruction(Inst, VecOS, Fixups, STI);
+  }
 
   // If we are showing fixups, create symbolic markers in the encoded
   // representation. We do this by making a per-bit map to the fixup item index,
diff --git a/lib/MC/MCContext.cpp b/lib/MC/MCContext.cpp
index bd2c4e960a..3a8cfaa947 100644
--- a/lib/MC/MCContext.cpp
+++ b/lib/MC/MCContext.cpp
@@ -140,17 +140,15 @@ MCSymbol *MCContext::GetOrCreateSymbol(const Twine &Name) {
 }
 
 MCSymbol *MCContext::CreateLinkerPrivateTempSymbol() {
-  SmallString<128> NameSV;
-  raw_svector_ostream(NameSV)
-    << MAI->getLinkerPrivateGlobalPrefix() << "tmp" << NextUniqueID++;
-  return CreateSymbol(NameSV);
+  small_string_ostream<128> NameSV;
+  NameSV << MAI->getLinkerPrivateGlobalPrefix() << "tmp" << NextUniqueID++;
+  return CreateSymbol(NameSV.str());
 }
 
 MCSymbol *MCContext::CreateTempSymbol() {
-  SmallString<128> NameSV;
-  raw_svector_ostream(NameSV)
-    << MAI->getPrivateGlobalPrefix() << "tmp" << NextUniqueID++;
-  return CreateSymbol(NameSV);
+  small_string_ostream<128> NameSV;
+  NameSV << MAI->getPrivateGlobalPrefix() << "tmp" << NextUniqueID++;
+  return CreateSymbol(NameSV.str());
 }
 
 unsigned MCContext::NextInstance(unsigned LocalLabelVal) {
diff --git a/lib/MC/MCDisassembler/Disassembler.cpp b/lib/MC/MCDisassembler/Disassembler.cpp
index 0530c26369..e3ec4eb30d 100644
--- a/lib/MC/MCDisassembler/Disassembler.cpp
+++ b/lib/MC/MCDisassembler/Disassembler.cpp
@@ -270,8 +270,7 @@ size_t LLVMDisasmInstruction(LLVMDisasmContextRef DCR, uint8_t *Bytes,
   const MCDisassembler *DisAsm = DC->getDisAsm();
   MCInstPrinter *IP = DC->getIP();
   MCDisassembler::DecodeStatus S;
-  SmallVector<char, 64> InsnStr;
-  raw_svector_ostream Annotations(InsnStr);
+  small_string_ostream<64> Annotations;
   S = DisAsm->getInstruction(Inst, Size, MemoryObject, PC,
                              /*REMOVE*/ nulls(), Annotations);
   switch (S) {
@@ -281,13 +280,10 @@ size_t LLVMDisasmInstruction(LLVMDisasmContextRef DCR, uint8_t *Bytes,
     return 0;
 
   case MCDisassembler::Success: {
-    Annotations.flush();
-    StringRef AnnotationsStr = Annotations.str();
-
     SmallVector<char, 64> InsnStr;
     raw_svector_ostream OS(InsnStr);
     formatted_raw_ostream FormattedOS(OS);
-    IP->printInst(&Inst, FormattedOS, AnnotationsStr);
+    IP->printInst(&Inst, FormattedOS, Annotations.str());
 
     if (DC->getOptions() & LLVMDisassembler_Option_PrintLatency)
       emitLatency(DC, Inst);
diff --git a/lib/MC/MCDwarf.cpp b/lib/MC/MCDwarf.cpp
index bddbf578d8..eab4d88f25 100644
--- a/lib/MC/MCDwarf.cpp
+++ b/lib/MC/MCDwarf.cpp
@@ -420,8 +420,7 @@ unsigned MCDwarfLineTableHeader::getFile(StringRef &Directory,
 void MCDwarfLineAddr::Emit(MCStreamer *MCOS, int64_t LineDelta,
                            uint64_t AddrDelta) {
   MCContext &Context = MCOS->getContext();
-  SmallString<256> Tmp;
-  raw_svector_ostream OS(Tmp);
+  small_string_ostream<256> OS;
   MCDwarfLineAddr::Encode(Context, LineDelta, AddrDelta, OS);
   MCOS->EmitBytes(OS.str());
 }
@@ -1647,8 +1646,7 @@ void MCDwarfFrameEmitter::Emit(MCObjectStreamer &Streamer, MCAsmBackend *MAB,
 void MCDwarfFrameEmitter::EmitAdvanceLoc(MCObjectStreamer &Streamer,
                                          uint64_t AddrDelta) {
   MCContext &Context = Streamer.getContext();
-  SmallString<256> Tmp;
-  raw_svector_ostream OS(Tmp);
+  small_string_ostream<256> OS;
   MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OS);
   Streamer.EmitBytes(OS.str());
 }
diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp
index fa5dfdc9fe..7bfbbf4932 100644
--- a/lib/MC/MCParser/AsmParser.cpp
+++ b/lib/MC/MCParser/AsmParser.cpp
@@ -4580,8 +4580,7 @@ bool AsmParser::parseMSInlineAsm(
   }
 
   // Build the IR assembly string.
-  std::string AsmStringIR;
-  raw_string_ostream OS(AsmStringIR);
+  string_ostream OS;
   const char *AsmStart = SrcMgr.getMemoryBuffer(0)->getBufferStart();
   const char *AsmEnd = SrcMgr.getMemoryBuffer(0)->getBufferEnd();
   array_pod_sort(AsmStrRewrites.begin(), AsmStrRewrites.end(), rewritesSort);
@@ -4646,8 +4645,7 @@ bool AsmParser::parseMSInlineAsm(
     }
     case AOK_DotOperator:
       // Insert the dot if the user omitted it.
-      OS.flush();
-      if (AsmStringIR.back() != '.')
+      if (OS.str().back() != '.')
         OS << '.';
       OS << AR.Val;
       break;