From 8c8e8c2e931b26905112faffb12f527f3256f5dc Mon Sep 17 00:00:00 2001
From: "Dwayne C. Litzenberger" <dlitz@dlitz.net>
Date: Mon, 16 Apr 2012 01:32:55 -0400
Subject: [PATCH] Fix bugs on 'unsigned char' platforms.

In ISO C++, the signedness of 'char' is undefined.  On some platforms (e.g.
ARM), 'char' is an unsigned type, but some of the code relies on 'char' being
signed (as it is on x86).  This is indicated by compiler warnings like this:

 bignum.h: In constructor 'CBigNum::CBigNum(char)':
 bignum.h:81:59: warning: comparison is always true due to limited range of data type [-Wtype-limits]

 util.cpp: In function 'bool IsHex(const string&)':
 util.cpp:427:28: warning: comparison is always false due to limited range of data type [-Wtype-limits]

In particular, IsHex erroneously returned true regardless of the input
characters, as long as the length of the string was a positive multiple of 2.

Note: For testing, it's possible using GCC to force char to be unsigned by
adding the -funsigned-char parameter to xCXXFLAGS.
---
 src/bignum.h  | 5 +++--
 src/script.h  | 6 ++++--
 src/uint256.h | 2 +-
 src/util.cpp  | 8 ++++----
 4 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/src/bignum.h b/src/bignum.h
index cea8e1e35..0d57dc8a8 100644
--- a/src/bignum.h
+++ b/src/bignum.h
@@ -78,7 +78,8 @@ public:
         BN_clear_free(this);
     }
 
-    CBigNum(char n)             { BN_init(this); if (n >= 0) setulong(n); else setint64(n); }
+    //CBigNum(char n) is not portable.  Use 'signed char' or 'unsigned char'.
+    CBigNum(signed char n)      { BN_init(this); if (n >= 0) setulong(n); else setint64(n); }
     CBigNum(short n)            { BN_init(this); if (n >= 0) setulong(n); else setint64(n); }
     CBigNum(int n)              { BN_init(this); if (n >= 0) setulong(n); else setint64(n); }
     CBigNum(long n)             { BN_init(this); if (n >= 0) setulong(n); else setint64(n); }
@@ -296,7 +297,7 @@ public:
             psz++;
 
         // hex string to bignum
-        static char phexdigit[256] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,1,2,3,4,5,6,7,8,9,0,0,0,0,0,0, 0,0xa,0xb,0xc,0xd,0xe,0xf,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0xa,0xb,0xc,0xd,0xe,0xf,0,0,0,0,0,0,0,0,0 };
+        static signed char phexdigit[256] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,1,2,3,4,5,6,7,8,9,0,0,0,0,0,0, 0,0xa,0xb,0xc,0xd,0xe,0xf,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0xa,0xb,0xc,0xd,0xe,0xf,0,0,0,0,0,0,0,0,0 };
         *this = 0;
         while (isxdigit(*psz))
         {
diff --git a/src/script.h b/src/script.h
index 524d08b3e..1aac324f6 100644
--- a/src/script.h
+++ b/src/script.h
@@ -268,7 +268,8 @@ public:
     }
 
 
-    explicit CScript(char b)           { operator<<(b); }
+    //explicit CScript(char b) is not portable.  Use 'signed char' or 'unsigned char'.
+    explicit CScript(signed char b)    { operator<<(b); }
     explicit CScript(short b)          { operator<<(b); }
     explicit CScript(int b)            { operator<<(b); }
     explicit CScript(long b)           { operator<<(b); }
@@ -285,7 +286,8 @@ public:
     explicit CScript(const std::vector<unsigned char>& b) { operator<<(b); }
 
 
-    CScript& operator<<(char b)           { return push_int64(b); }
+    //CScript& operator<<(char b) is not portable.  Use 'signed char' or 'unsigned char'.
+    CScript& operator<<(signed char b)    { return push_int64(b); }
     CScript& operator<<(short b)          { return push_int64(b); }
     CScript& operator<<(int b)            { return push_int64(b); }
     CScript& operator<<(long b)           { return push_int64(b); }
diff --git a/src/uint256.h b/src/uint256.h
index bf3c55bcc..104b84970 100644
--- a/src/uint256.h
+++ b/src/uint256.h
@@ -305,7 +305,7 @@ public:
             psz += 2;
 
         // hex string to uint
-        static char phexdigit[256] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,1,2,3,4,5,6,7,8,9,0,0,0,0,0,0, 0,0xa,0xb,0xc,0xd,0xe,0xf,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0xa,0xb,0xc,0xd,0xe,0xf,0,0,0,0,0,0,0,0,0 };
+        static unsigned char phexdigit[256] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,1,2,3,4,5,6,7,8,9,0,0,0,0,0,0, 0,0xa,0xb,0xc,0xd,0xe,0xf,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0xa,0xb,0xc,0xd,0xe,0xf,0,0,0,0,0,0,0,0,0 };
         const char* pbegin = psz;
         while (phexdigit[(unsigned char)*psz] || *psz == '0')
             psz++;
diff --git a/src/util.cpp b/src/util.cpp
index 19e48d3bd..9f2de3449 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -425,7 +425,7 @@ bool ParseMoney(const char* pszIn, int64& nRet)
 }
 
 
-static char phexdigit[256] =
+static signed char phexdigit[256] =
 { -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
   -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
   -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
@@ -461,12 +461,12 @@ vector<unsigned char> ParseHex(const char* psz)
     {
         while (isspace(*psz))
             psz++;
-        char c = phexdigit[(unsigned char)*psz++];
-        if (c == (char)-1)
+        signed char c = phexdigit[(unsigned char)*psz++];
+        if (c == (signed char)-1)
             break;
         unsigned char n = (c << 4);
         c = phexdigit[(unsigned char)*psz++];
-        if (c == (char)-1)
+        if (c == (signed char)-1)
             break;
         n |= c;
         vch.push_back(n);