[MC] - Don't assert when non-english characters are used.

[grimar]

Summary

I found that llvm-mc does not like non-english characters even in comments,
which it tries to tokenize.

Problem happens because of functions like isdigit(), isalnum() which takes
int argument and expects it is not negative.
But at the same time MCParser uses char* to store input buffer poiner, char has signed value,
so it is possible to pass negative value to one of functions from above and
that triggers an assert.
Testcase for demonstration is provided.

To fix the issue helper functions were introduced in StringExtras.h.

[davide]

Indeed isdigit should have its argument converted to uchar proor to the call but, is the result you get from mc correct? http://en.cppreference.com/w/cpp/string/byte/isdigit

If so, can you please check the output in your test?

[grimar]

Yes, output is correct. Updated testcase as requested.

[rnk]

cppreference suggests writing our own wrapper to avoid this issue: http://en.cppreference.com/w/cpp/string/byte/isdigit

I'd suggest adding llvm::isDigit and llvm::isHexDigit in StringExtras.h next to our other hex digit conversion routines, so we don't have to repeat this surprising cast everywhere.

[davide]

In D38461#885923, @rnk wrote:

cppreference suggests writing our own wrapper to avoid this issue: http://en.cppreference.com/w/cpp/string/byte/isdigit

I'd suggest adding llvm::isDigit and llvm::isHexDigit in StringExtras.h next to our other hex digit conversion routines, so we don't have to repeat this surprising cast everywhere.

Yes, that sounds the best solution actually.

[grimar]

• Added helpers to StringExtras as was suggested.

[ruiu]

LGTM

lib/MC/MCParser/AsmLexer.cpp

 
 /// LexFloatLiteral: [0-9]*[.][0-9]*([eE][+-]?[0-9]*)?
 ///
 /// The leading integral digit sequence and dot should have already been
 /// consumed, some or all of the fractional digit sequence *can* have been
 /// consumed.
 AsmToken AsmLexer::LexFloatLiteral() {
   // Skip the fractional digit sequence.
-  while (isdigit(*CurPtr))
+  while (isdigit(static_cast<unsigned char>(*CurPtr)))
     ++CurPtr;
 
   // Check for exponent; we intentionally accept a slighlty wider set of
   // literals here and rely on the upstream client to reject invalid ones (e.g.,
   // "1e+").
   if (*CurPtr == 'e' || *CurPtr == 'E') {
     ++CurPtr;
     if (*CurPtr == '-' || *CurPtr == '+')
       ++CurPtr;
-    while (isdigit(*CurPtr))
+    while (isdigit(static_cast<unsigned char>(*CurPtr)))
       ++CurPtr;
   }
 
   return AsmToken(AsmToken::Real,
                   StringRef(TokStart, CurPtr - TokStart));
 }
 
 /// LexHexFloatLiteral matches essentially (.[0-9a-fA-F]*)?[pP][+-]?[0-9a-fA-F]+
 /// while making sure there are enough actual digits around for the constant to
 /// be valid.
 ///
 /// The leading "0x[0-9a-fA-F]*" (i.e. integer part) has already been consumed
 /// before we get here.
 AsmToken AsmLexer::LexHexFloatLiteral(bool NoIntDigits) {
   assert((*CurPtr == 'p' || *CurPtr == 'P' || *CurPtr == '.') &&
          "unexpected parse state in floating hex");
   bool NoFracDigits = true;
 
   // Skip the fractional part if there is one
   if (*CurPtr == '.') {
     ++CurPtr;
 
     const char *FracStart = CurPtr;
-    while (isxdigit(*CurPtr))
+    while (isxdigit(static_cast<unsigned char>(*CurPtr)))
       ++CurPtr;
 
     NoFracDigits = CurPtr == FracStart;
   }
 
   if (NoIntDigits && NoFracDigits)
     return ReturnError(TokStart, "invalid hexadecimal floating-point constant: "
                                  "expected at least one significand digit");
 
   // Make sure we do have some kind of proper exponent part
   if (*CurPtr != 'p' && *CurPtr != 'P')
     return ReturnError(TokStart, "invalid hexadecimal floating-point constant: "
                                  "expected exponent part 'p'");
   ++CurPtr;
 
   if (*CurPtr == '+' || *CurPtr == '-')
     ++CurPtr;
 
   // N.b. exponent digits are *not* hex
   const char *ExpStart = CurPtr;
-  while (isdigit(*CurPtr))
+  while (isdigit(static_cast<unsigned char>(*CurPtr)))
     ++CurPtr;
 
   if (CurPtr == ExpStart)
     return ReturnError(TokStart, "invalid hexadecimal floating-point constant: "
                                  "expected at least one exponent digit");
 
   return AsmToken(AsmToken::Real, StringRef(TokStart, CurPtr - TokStart));
 }
 
 /// LexIdentifier: [a-zA-Z_.][a-zA-Z0-9_$.@?]*
 static bool IsIdentifierChar(char c, bool AllowAt) {
-  return isalnum(c) || c == '_' || c == '$' || c == '.' ||
-         (c == '@' && AllowAt) || c == '?';
+  return isalnum(static_cast<unsigned char>(c)) || c == '_' || c == '$' ||
+         c == '.' || (c == '@' && AllowAt) || c == '?';
 }
 
 AsmToken AsmLexer::LexIdentifier() {
   // Check for floating point literals.
-  if (CurPtr[-1] == '.' && isdigit(*CurPtr)) {
+  if (CurPtr[-1] == '.' && isdigit(static_cast<unsigned char>(*CurPtr))) {
     // Disambiguate a .1243foo identifier from a floating literal.
-    while (isdigit(*CurPtr))
+    while (isdigit(static_cast<unsigned char>(*CurPtr)))
       ++CurPtr;
     if (*CurPtr == 'e' || *CurPtr == 'E' ||
         !IsIdentifierChar(*CurPtr, AllowAtInIdentifier))
       return LexFloatLiteral();
   }
 
   while (IsIdentifierChar(*CurPtr, AllowAtInIdentifier))
     ++CurPtr;

 }
 
 // Look ahead to search for first non-hex digit, if it's [hH], then we treat the
 // integer as a hexadecimal, possibly with leading zeroes.
 static unsigned doLookAhead(const char *&CurPtr, unsigned DefaultRadix) {
   const char *FirstHex = nullptr;
   const char *LookAhead = CurPtr;
   while (true) {
-    if (isdigit(*LookAhead)) {
+    if (isdigit(static_cast<unsigned char>(*LookAhead))) {
       ++LookAhead;
-    } else if (isxdigit(*LookAhead)) {
+    } else if (isxdigit(static_cast<unsigned char>(*LookAhead))) {
       if (!FirstHex)
         FirstHex = LookAhead;
       ++LookAhead;
     } else {
       break;
     }
   }
   bool isHex = *LookAhead == 'h' || *LookAhead == 'H';

 ///   Decimal integer: [1-9][0-9]*
 AsmToken AsmLexer::LexDigit() {
   // MASM-flavor binary integer: [01]+[bB]
   // MASM-flavor hexadecimal integer: [0-9][0-9a-fA-F]*[hH]
   if (IsParsingMSInlineAsm && isdigit(CurPtr[-1])) {
     const char *FirstNonBinary = (CurPtr[-1] != '0' && CurPtr[-1] != '1') ?
                                    CurPtr - 1 : nullptr;
     const char *OldCurPtr = CurPtr;
-    while (isxdigit(*CurPtr)) {
+    while (isxdigit(static_cast<unsigned char>(*CurPtr))) {
       if (*CurPtr != '0' && *CurPtr != '1' && !FirstNonBinary)
         FirstNonBinary = CurPtr;
       ++CurPtr;
     }
 
     unsigned Radix = 0;
     if (*CurPtr == 'h' || *CurPtr == 'H') {
       // hexadecimal number
if (CurPtr[-1] != '0' || CurPtr[0] == '.') {
     SkipIgnoredIntegerSuffix(CurPtr);
 
     return intToken(Result, Value);
   }
 
   if (!IsParsingMSInlineAsm && ((*CurPtr == 'b') || (*CurPtr == 'B'))) {
     ++CurPtr;
     // See if we actually have "0b" as part of something like "jmp 0b\n"
-    if (!isdigit(CurPtr[0])) {
+    if (!isdigit(static_cast<unsigned char>(CurPtr[0]))) {
       --CurPtr;
       StringRef Result(TokStart, CurPtr - TokStart);
       return AsmToken(AsmToken::Integer, Result, 0);
     }
     const char *NumStart = CurPtr;
     while (CurPtr[0] == '0' || CurPtr[0] == '1')
       ++CurPtr;
 
if (!IsParsingMSInlineAsm && ((*CurPtr == 'b') || (*CurPtr == 'B'))) {
     SkipIgnoredIntegerSuffix(CurPtr);
 
     return intToken(Result, Value);
   }
 
   if ((*CurPtr == 'x') || (*CurPtr == 'X')) {
     ++CurPtr;
     const char *NumStart = CurPtr;
-    while (isxdigit(CurPtr[0]))
+    while (isxdigit(static_cast<unsigned char>(CurPtr[0])))
       ++CurPtr;
 
     // "0x.0p0" is valid, and "0x0p0" (but not "0xp0" for example, which will be
     // diagnosed by LexHexFloatLiteral).
     if (CurPtr[0] == '.' || CurPtr[0] == 'p' || CurPtr[0] == 'P')
       return LexHexFloatLiteral(NumStart == CurPtr);
 
     // Otherwise requires at least one hex digit.

test/MC/AsmParser/non-english-characters.s

+# RUN: llvm-mc -triple i386-linux-gnu < %s > %t
+# 0bﾑ
+# 0xﾑ
+# .ﾑ4
+# .Xﾑ
+# .1ﾑ
+# .1eﾑ
+# 0x.ﾑ
+# 0x0pﾑ
+.intel_syntax
+# 1ﾑ