From 52661f08b97ed2792a1afa56f583c2bef5295cfd Mon Sep 17 00:00:00 2001
From: Moraxyc <i@qaq.li>
Date: Sat, 27 Dec 2025 23:31:52 +0800
Subject: [PATCH] _9base: fix build with c23

---
 .../_9/_9base/fix-build-with-c23.patch        | 101 ++++++++++++++++++
 pkgs/by-name/_9/_9base/package.nix            |   4 +
 2 files changed, 105 insertions(+)
 create mode 100644 pkgs/by-name/_9/_9base/fix-build-with-c23.patch

diff --git a/pkgs/by-name/_9/_9base/fix-build-with-c23.patch b/pkgs/by-name/_9/_9base/fix-build-with-c23.patch
new file mode 100644
index 000000000000..f8f58d6c5f9b
--- /dev/null
+++ b/pkgs/by-name/_9/_9base/fix-build-with-c23.patch
@@ -0,0 +1,101 @@
+From ba9e372f3165e0cfd73fcc8a1352fbb790ea2439 Mon Sep 17 00:00:00 2001
+From: Moraxyc <i@qaq.li>
+Date: Sat, 27 Dec 2025 23:22:47 +0800
+Subject: [PATCH] fix build with c23
+
+---
+ dd/dd.c    |  4 ++--
+ troff/n5.c | 24 ++++++++++++------------
+ 2 files changed, 14 insertions(+), 14 deletions(-)
+
+diff --git a/dd/dd.c b/dd/dd.c
+index 9e69b6b..1e7d4c5 100644
+--- a/dd/dd.c
++++ b/dd/dd.c
+@@ -312,11 +312,11 @@ match(char *s)
+ 	cs = string;
+ 	while(*cs++ == *s)
+ 		if(*s++ == '\0')
+-			goto true;
++			goto match_true;
+ 	if(*s != '\0')
+ 		return 0;
+ 
+-true:
++match_true:
+ 	cs--;
+ 	string = cs;
+ 	return 1;
+diff --git a/troff/n5.c b/troff/n5.c
+index 7266432..7566068 100644
+--- a/troff/n5.c
++++ b/troff/n5.c
+@@ -642,15 +642,15 @@ void caseif(void)
+ void caseif1(int x)
+ {
+ 	extern int falsef;
+-	int notflag, true;
++	int notflag, truev;
+ 	Tchar i;
+ 
+ 	if (x == 2) {
+ 		notflag = 0;
+-		true = iflist[ifx];
++		truev = iflist[ifx];
+ 		goto i1;
+ 	}
+-	true = 0;
++	truev = 0;
+ 	skip();
+ 	if ((cbits(i = getch())) == '!') {
+ 		notflag = 1;
+@@ -663,37 +663,37 @@ void caseif1(int x)
+ 	ifnum = 0;
+ 	if (!nonumb) {
+ 		if (i > 0)
+-			true++;
++			truev++;
+ 		goto i1;
+ 	}
+ 	i = getch();
+ 	switch (cbits(i)) {
+ 	case 'e':
+ 		if (!(numtabp[PN].val & 01))
+-			true++;
++			truev++;
+ 		break;
+ 	case 'o':
+ 		if (numtabp[PN].val & 01)
+-			true++;
++			truev++;
+ 		break;
+ 	case 'n':
+ 		if (NROFF)
+-			true++;
++			truev++;
+ 		break;
+ 	case 't':
+ 		if (TROFF)
+-			true++;
++			truev++;
+ 		break;
+ 	case ' ':
+ 		break;
+ 	default:
+-		true = cmpstr(i);
++		truev = cmpstr(i);
+ 	}
+ i1:
+-	true ^= notflag;
++	truev ^= notflag;
+ 	if (x == 1)
+-		iflist[ifx] = !true;
+-	if (true) {
++		iflist[ifx] = !truev;
++	if (truev) {
+ i2:
+ 		while ((cbits(i = getch())) == ' ')
+ 			;
+-- 
+2.51.2
+
diff --git a/pkgs/by-name/_9/_9base/package.nix b/pkgs/by-name/_9/_9base/package.nix
index e4cd519d3aaa..2b4f76e55f42 100644
--- a/pkgs/by-name/_9/_9base/package.nix
+++ b/pkgs/by-name/_9/_9base/package.nix
@@ -29,6 +29,10 @@ stdenv.mkDerivation {
     # https://github.com/9fans/plan9port/commit/540caa5873bcc3bc2a0e1896119f5b53a0e8e630
     # https://github.com/9fans/plan9port/commit/323e1a8fac276f008e6d5146a83cbc88edeabc87
     ./getcallerpc-use-macro-or-stub.patch
+    # fix build with c23
+    #   dd.c:315:30: error: expected identifier or '*' before 'true'
+    #   n5.c:690:22: error: lvalue required as left operand of assignment
+    ./fix-build-with-c23.patch
   ]
   ++ patches;