slist.disconnect: -Wmaybe-uninitialized

ci-all.sh

@@ -4,12 +4,15 @@ make -j9
 make -j4 CXX='g++ -std=c++03' CFLAGS=-I.
 make -j4 CXX='g++ -std=c++11' CFLAGS=-I.
 make -j4 CXX='g++ -std=c++17' CFLAGS=-I.
+make -j4 CXX='g++ -std=c++20' CFLAGS=-I.
+make -j4 CXX='g++ -std=c++23' CFLAGS=-I.
 make -j9 LONG=1 O0=1 SANITIZE=1
 make -j9 LONG=1 O1=1 SANITIZE=1
 make -j9 LONG=1 O2=1 SANITIZE=1
 make -j9 LONG=1 O3=1 SANITIZE=1
 make -j9 LONG=1 Og=1 SANITIZE=1
 make -j9 LONG=1 Os=1 SANITIZE=1
+make -j9 DEBUG=1
 make -j9 LONG=1 Ofast=1
 make -j9 LONG=1 O0=1 SANITIZE=0
 make -j9 LONG=1 O1=1 SANITIZE=0
@@ -20,12 +23,16 @@ make -j9 LONG=1 Os=1 SANITIZE=0
 make -j9 LONG=1 Ofast=1 SANITIZE=0
 make -j9 CC=gcc\ -std=c99
 make -j9 CC=gcc\ -std=c11
+make -j9 CC=gcc\ -std=c17
+make -j9 CC=gcc\ -std=c2x
 make -j9 CXX='clang++ -stdlib=libc++'
 make -j9 CXX='clang++ -std=c++11 -stdlib=libc++'
 make -j9 CXX='clang++ -std=c++17 -stdlib=libc++'
 make -j9 CXX='clang++ -std=c++20 -stdlib=libc++'
+make -j9 CXX='clang++ -std=c++23 -stdlib=libc++'
 make -j9 CC=clang CXX='clang++ -std=c++11'
 make -j9 CC=clang CXX='clang++ -std=c++17'
 make -j9 CC=clang CXX='clang++ -std=c++20'
+make -j9 CC=clang CXX='clang++ -std=c++23'
 make examples SANITIZE=1
 make examples SANITIZE=0

ctl/forward_list.h

@@ -243,7 +243,7 @@ static inline void JOIN(A, disconnect)(A *self, B *node)
         self->head = self->head->next;
     else
     {
-        B *prev;
+        B *prev = self->head;
         for (B *tail = self->head; tail != node; prev = tail, tail = tail->next)
             ;
         if (prev->next) // == node