From a498f851ef2f50c9b8ac47e238137af52b54057d Mon Sep 17 00:00:00 2001
From: lemon <lsof@mailbox.org>
Date: Sun, 1 Mar 2026 13:35:45 +0100
Subject: cpp: fix token spacing edge case when empty macros are involved

---
 c/lex.c      | 6 +++++-
 test/07-pp.c | 5 +++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/c/lex.c b/c/lex.c
index 5ff30a2..07b5cb0 100644
--- a/c/lex.c
+++ b/c/lex.c
@@ -1214,8 +1214,10 @@ expandfnmacro(struct lexer *lx, struct span *span, internstr mname, struct macro
          arg->idx2 = argsbuf.n;
          arg->nfirstx = arg->nlastx = 1;
          int ilastx = -1;
-         for (;;) {
+         for (bool pad = 0;;) {
+            struct macrostack *sprev = lx->macstk;
             if (!advancemacstk(lx, &tk)) {
+               pad |= tk.space && lx->macstk == sprev; /* preserve whitespace empty macro */
                if (lx->macstk == l && l->idx == 1)
                   arg->nfirstx = argsbuf.n - arg->idx2;
                if (lx->macstk == l+1 && lx->macstk->idx == 0 && l->idx == l->rl.n)
@@ -1224,8 +1226,10 @@ expandfnmacro(struct lexer *lx, struct span *span, internstr mname, struct macro
             }
             if (tk.t == TKEOF) break;
             size_t off = l->rl.p - argsbuf.p;
+            tk.space |= pad;
             vpush(&argsbuf, tk);
             l->rl.p = argsbuf.p + off;
+            pad = 0;
          }
          arg->n2 = argsbuf.n - arg->idx2;
          arg->nlastx = ilastx < 0 ? 1 : args->n2 - ilastx;
diff --git a/test/07-pp.c b/test/07-pp.c
index 2458111..47fb959 100644
--- a/test/07-pp.c
+++ b/test/07-pp.c
@@ -12,7 +12,7 @@ ok ...
 token spacing:
 ++ -- ++ === (0)~> ++ 3>0$
 sum = 1 + 2 +3;$
-[ baz]$
+[ baz] ;$
 +. *$
 */
 
@@ -121,7 +121,8 @@ S\
 #define foo bar
 #define bar EMPTY baz
 #define EMPTY
-        xstr([foo] EMPTY) "$\n"
+#define EMPTY2 EMPTY
+        xstr([foo] EMPTY2;) "$\n"
 #define qx1(...)/**/__VA_ARGS__
 #define qx2(a) qx1 ( a )
         xstr(+qx2 ( .)//
-- 
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