From 98222b7c0506b0a9833230177b939f8c25046b31 Mon Sep 17 00:00:00 2001
From: lemon <lsof@mailbox.org>
Date: Tue, 14 Apr 2026 12:05:57 +0200
Subject: cpp: concat 123 ## .

---
 src/c.c      |  3 ++-
 src/c_lex.c  | 20 +++++++++++++++++---
 test/07-pp.c |  4 ++--
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/src/c.c b/src/c.c
index 0ae12d9..2d51bd2 100644
--- a/src/c.c
+++ b/src/c.c
@@ -163,7 +163,8 @@ isexprtok(CComp *cm)
 #define tk(x) [x] = 1
          tk('+'), tk('-'), tk('*'), tk('&'), tk('~'), tk('!'), tk(TKINC), tk(TKDEC),
          tk(TKWsizeof), tk(TKW_Alignof), tk(TKWalignof), tk(TKWtrue), tk(TKWfalse),
-         tk('('), tk(TKNUMLIT), tk(TKCHRLIT), tk(TKSTRLIT), tk(TKW_Generic)
+         tk('('), tk(TKNUMLIT), tk(TKCHRLIT), tk(TKSTRLIT), tk(TKW_Generic),
+         tk(TKW__builtin_va_arg),
 #undef tk
       };
       return tk.t < countof(tks) && tks[tk.t];
diff --git a/src/c_lex.c b/src/c_lex.c
index c5e16aa..6370a1c 100644
--- a/src/c_lex.c
+++ b/src/c_lex.c
@@ -819,6 +819,12 @@ tokpaste(Lexer *lx, Token *dst, const Token *l, const Token *r)
    } else if (l->t == TKNUMLIT && (isppident(*r) || r->t == TKNUMLIT)) {
       /* 0x ## abc   ;   213 ## 456 */
       t = TKNUMLIT;
+   } else if (l->t == '.' && r->t == TKNUMLIT) {
+      /* . ## 123 */
+      t = TKNUMLIT;
+   } else if (l->t == TKNUMLIT && r->t == '.') {
+      /* 123 ## . */
+      t = TKNUMLIT;
    } else if (l->t && !r->t) {
       if (dst) *dst = *l;
       return 1;
@@ -855,10 +861,18 @@ tokpaste(Lexer *lx, Token *dst, const Token *l, const Token *r)
    if (dst->span.ex.file == r->span.ex.file && dst->span.ex.off < r->span.ex.off)
       joinspan(&dst->span.ex, r->span.ex);
    dst->t = t;
-   dst->len = l->len + r->len;
+
+   int n1, n2;
+   const char *s1, *s2;
+   if (l->t == '.') n1 = 1, s1 = ".";
+   else n1 = l->len, s1 = l->s;
+   if (r->t == '.') n2 = 1, s2 = ".";
+   else n2 = r->len, s2 = r->s;
+
+   dst->len = n1 + n2;
    char *s = (isppident(*dst) && dst->len + 1 < sizeof buf) ? buf : alloc(lx->tmparena, dst->len + 1, 1);
-   memcpy(s, l->s, l->len);
-   memcpy(s + l->len, r->s, r->len);
+   memcpy(s, s1, n1);
+   memcpy(s + n1, s2, n2);
    s[dst->len] = 0;
    dst->space = l->space;
    if (isppident(*dst)) {
diff --git a/test/07-pp.c b/test/07-pp.c
index 4301dbd..7370413 100644
--- a/test/07-pp.c
+++ b/test/07-pp.c
@@ -14,7 +14,7 @@ token spacing:
 sum = 1 + 2 +3;$
 [ baz] ;$
 +. *$
-x=7
+x=7 7
 */
 
 #include "07-pp.h"
@@ -138,7 +138,7 @@ qx2(*) ) "$\n"
          3
 #endif
       );
-   printf("x=%d\n",x);
+   printf("x=%d %g\n",x, CAT(7,.));
 
    CAT(ret,urn) 0;
 }
-- 
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