Source: Avoid out-of-range inputs to std::isspace()

`isspace` takes `int` but documents that the value must be representable
by `unsigned char`, or be EOF.  Use a wrapper to cast to `unsigned char`
to avoid sign extension while converting to `int`.  This generalizes the
fix from commit 5e8c176e2a (cmExecuteProcessCommand: Cast c to unsigned
char before cast to int, 2024-01-05) to other `isspace` call sites.

This was detected by assertions in the MSVC standard library while
processing UTF-8 text.

Issue: #25561

1 files changed, 2 insertions, 2 deletions

diff --git a/Source/cmSystemTools.cxx b/Source/cmSystemTools.cxx
index 1b3dbe2..fca8186 100644
--- a/Source/cmSystemTools.cxx
+++ b/Source/cmSystemTools.cxx
@@ -486,7 +486,7 @@ bool cmSystemTools::SplitProgramFromArgs(std::string const& command,
   const char* c = command.c_str();
 
   // Skip leading whitespace.
-  while (isspace(static_cast<unsigned char>(*c))) {
+  while (cmIsSpace(*c)) {
     ++c;
   }
 
@@ -516,7 +516,7 @@ bool cmSystemTools::SplitProgramFromArgs(std::string const& command,
       in_double = true;
     } else if (*c == '\'') {
       in_single = true;
-    } else if (isspace(static_cast<unsigned char>(*c))) {
+    } else if (cmIsSpace(*c)) {
       break;
     } else {
       program += *c;