all: enhance CMake tests; assorted updates

src/util/system_features.h

@@ -30,7 +30,7 @@
 
 #if defined(__has_include)
 #if __has_include(<features.h>)
-#include <features.h> // for __GLIBC__
+#include <features.h> // for __GLIBC__ and __GLIBC_MINOR__
 #endif
 #endif
 
@@ -42,8 +42,8 @@
 #endif
 #endif // _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
 
-#if 0 // TODO later
 // libc++ hardenining
+#if defined(__cplusplus) && 0 // TODO later
 #if defined(__clang__) && defined(__clang_major__) && (__clang_major__ + 0 >= 18)
 #if DEBUG
 #define _LIBCPP_HARDENING_MODE _LIBCPP_HARDENING_MODE_DEBUG

src/util/system_headers.h

@@ -29,7 +29,7 @@
 #include "system_defs.h"
 
 #if !(__cplusplus + 0 >= 201703L)
-#error "C++17 is required"
+#error "FATAL ERROR: C++17 is required"
 #endif
 
 // check expected defines

src/util/util.cpp

@@ -254,6 +254,12 @@ TEST_CASE("ptr_check_no_overlap 3") {
 // stdlib
 **************************************************************************/
 
+const char *upx_getenv(const char *envvar) noexcept {
+    if (envvar != nullptr && envvar[0])
+        return ::getenv(envvar);
+    return nullptr;
+}
+
 int upx_rand(void) noexcept { return ::rand(); }
 
 void *upx_calloc(size_t n, size_t element_size) may_throw {
@@ -430,7 +436,7 @@ struct TestSortAllPermutations {
             memcpy(a, perm, sizeof(*a) * n);
             sort(a, n, sizeof(*a), CompareFunc);
             for (size_t i = 0; i < n; i++)
-                assert_noexcept((a[i] == 255 + i));
+                assert_noexcept(a[i] == 255 + i);
             num_perms += 1;
         } while (std::next_permutation(perm, perm + n));
         return num_perms;
@@ -774,11 +780,11 @@ int fn_strcmp(const char *n1, const char *n2) {
 
 // UPX convention: any environment variable that is set and is not strictly equal to "0" is true
 bool is_envvar_true(const char *envvar, const char *alternate_name) noexcept {
-    const char *e = getenv(envvar);
+    const char *e = upx_getenv(envvar);
     if (e != nullptr && e[0])
         return strcmp(e, "0") != 0;
     if (alternate_name != nullptr) {
-        e = getenv(alternate_name);
+        e = upx_getenv(alternate_name);
         if (e != nullptr && e[0])
             return strcmp(e, "0") != 0;
     }

src/util/util.h

@@ -145,6 +145,8 @@ inline void ptr_invalidate_and_poison(T *(&ptr)) noexcept {
 
 noinline void *upx_calloc(size_t n, size_t element_size) may_throw;
 
+noinline const char *upx_getenv(const char *envvar) noexcept;
+
 void upx_memswap(void *a, void *b, size_t bytes) noexcept;
 
 noinline int upx_rand(void) noexcept;