Avoid using isspace() with signed characters

"char" is signed by default on many systems, so when using a "char"
variable as input to isspace(), which takes an "int" parameter, the
parameter gets sign-extended. Now in some libc implementations, the
isspace() function is implemented as a macro that directly indexes
an array for looking up the result - which might go wrong, of course,
if the byte values has the highest bit set. So when compiling Hatari
with Cygwin, there are the following compiler warnings:

.../build68k.c: In function ‘main’:
.../build68k.c:314:18: warning: array subscript has type ‘char’ [-Wchar-subscripts]
  314 |   while (isspace(*opstrp))
      |                  ^~~~~~~
.../build68k.c:319:18: warning: array subscript has type ‘char’ [-Wchar-subscripts]
  319 |    if (!isspace (*osendp))
      |                  ^~~~~~~
.../build68k.c:331:19: warning: array subscript has type ‘char’ [-Wchar-subscripts]
  331 |   while (!isspace(*p++));
      |                   ^~~~

Thus let's make sure to cast the "char" to unsigned first before using
it as parameter to the isspace() function.

diff --git a/build68k.cpp b/build68k.cpp
index 82ad4fb31f9259e90892426e7dab92d42573c8b0..4b5e8c16b87ce3d6e31704b3dfc745426ecce414 100644 (file)
--- a/build68k.cpp
+++ b/build68k.cpp
@@ -311,12 +311,12 @@ int main(int argc, char **argv)
                char tmp[100], *p;
                int slen = 0;
 
-               while (isspace(*opstrp))
+               while (isspace((unsigned char)*opstrp))
                        opstrp++;
 
                osendp = opstrp;
                while (*osendp) {
-                       if (!isspace (*osendp))
+                       if (!isspace ((unsigned char)*osendp))
                                slen = osendp - opstrp + 1;
                        osendp++;
                }
@@ -328,7 +328,7 @@ int main(int argc, char **argv)
                strcpy (tmp, opstrp);
                strcat (tmp, " ");
                p = tmp;
-               while (!isspace(*p++));
+               while (!isspace((unsigned char)*p++));
                *p = 0;
                printf("/* %s */\n", tmp);
                printf("{0x%04X,%2d,{", bitpattern, n_variable);