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llvm-undname: Improve string literal demangling with embedded \0 chars 

- Don't assert when a string looks like a u32 string to the heuristic
  but doesn't have a length that's 0 mod 4.  Instead, classify those
  as u16 with embedded \0 chars. Found by oss-fuzz.
- Print embedded nul bytes as \0 instead of \x00.

llvm-svn: 358835
This commit is contained in:
Nico Weber 2019-04-20 23:59:06 +00:00
parent f2654b638d
commit 8eeaf5178d
2 changed files with 15 additions and 2 deletions
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7
llvm/lib/Demangle/MicrosoftDemangle.cpp
View File

@ -1088,6 +1088,9 @@ static void outputHex(OutputStream &OS, unsigned C) {
static void outputEscapedChar(OutputStream &OS, unsigned C) {
switch (C) {
case '\0': // nul
OS << "\\0";
return;
case '\'': // single quote
OS << "\\\'";
return;
@ -1165,7 +1168,7 @@ static unsigned guessCharByteSize(const uint8_t *StringBytes, unsigned NumChars,
// 2-byte, or 4-byte null terminator.
if (NumBytes < 32) {
unsigned TrailingNulls = countTrailingNullBytes(StringBytes, NumChars);
if (TrailingNulls >= 4)
if (TrailingNulls >= 4 && NumBytes % 4 == 0)
return 4;
if (TrailingNulls >= 2)
return 2;
@ -1179,7 +1182,7 @@ static unsigned guessCharByteSize(const uint8_t *StringBytes, unsigned NumChars,
// perfect and is biased towards languages that have ascii alphabets, but this
// was always going to be best effort since the encoding is lossy.
unsigned Nulls = countEmbeddedNulls(StringBytes, NumChars);
if (Nulls >= 2 * NumChars / 3)
if (Nulls >= 2 * NumChars / 3 && NumBytes % 4 == 0)
return 4;
if (Nulls >= NumChars / 3)
return 2;

10
llvm/test/Demangle/ms-string-literals.test
View File

@ -771,3 +771,13 @@
??_C@_0CG@HJGBPLNO@l?$AAo?$AAo?$AAk?$AAA?$AAh?$AAe?$AAa?$AAd?$AAH?$AAa?$AAr?$AAd?$AAB?$AAr?$AAe?$AA@
; CHECK: u"lookAheadHardBre"...
; These are u16 strings that the diagnostic would classify as u32 -- except
; that their byte length % 4 is 2, so they can't be u32.
??_C@_05LABPAAN@b?$AA?$AA?$AA?$AA?$AA@
; CHECK: u"b\0"
??_C@_0CC@MBPKDIAM@a?$AA?$AA?$AAb?$AA?$AA?$AAc?$AA?$AA?$AAd?$AA?$AA?$AAe?$AA?$AA?$AAf?$AA?$AA?$AAg?$AA?$AA?$AAh?$AA?$AA?$AA@
; CHECK: u"a\0b\0c\0d\0e\0f\0g\0h\0"...