Fix next_code_point<char16_t>; #576

gdb/2024-12-unicode-fuzz-tests.gdb

@@ -0,0 +1,8 @@
+source ../gdb/functions.gdb
+
+delete breakpoints
+chain tests/unicode_test.cpp:6943
+chain tests/unicode_fuzz.hpp:29
+chain webpp/unicode/normalization.hpp:697
+chain webpp/unicode/normalization.hpp:442
+

gdb/functions.gdb

@@ -0,0 +1,23 @@
+set $bpstart = $bpnum ? $bpnum : 0
+set breakpoint pending on
+
+define chain
+  break $arg0
+
+  set $distance = $bpnum - $bpstart
+
+  commands $bpnum
+    set $nextbp = $_hit_bpnum + 1
+    set $chain_num = $_hit_bpnum - $bpstart
+    printf "\nWe're at breakpoint number %d of the chain\n", $chain_num
+    printf "Enabling breakpoint:  %d\n\n", $nextbp
+    enable once $nextbp
+  end
+
+  # don't disable the first one
+  if $distance > 1
+    printf "Distabling:  %d\n", $bpnum
+    disable $bpnum
+  end
+end
+

webpp/unicode/unicode.hpp

@@ -1028,7 +1028,9 @@ namespace webpp::unicode {
                         code_point += 0x1'0000U;
                     }
                     if (error || is_surrogate(code_point)) [[unlikely]] {
-                        --pos;
+                        if (requires_2_units) {
+                            --pos;
+                        }
                         code_point = cu1;
                         break;
                     }