From 497289eb02927c75f6e77bba052bec2a4589c227 Mon Sep 17 00:00:00 2001
From: lemon <lsof@mailbox.org>
Date: Sat, 20 Dec 2025 22:00:28 +0100
Subject: lexer: note source of #include when error occurs in #included file

---
 c/lex.c | 6 ++++++
 c/lex.h | 3 ++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/c/lex.c b/c/lex.c
index 5c627f1..6fa6fa3 100644
--- a/c/lex.c
+++ b/c/lex.c
@@ -1507,6 +1507,7 @@ tryinclude(struct lexer *lx, const struct span *span, char *path)
       /* fallthru */
    case LXOK:
       new.save = xmalloc(sizeof *new.save);
+      lx->inclnerror = nerror;
       memcpy(new.save, lx, sizeof *lx);
       *lx = new;
 
@@ -1850,6 +1851,11 @@ Begin:
                markfileonce(lx->fileid, lx->inclguard);
             }
             struct lexer *sv = lx->save;
+            if (sv->inclnerror != nerror) {
+               int line;
+               const char *f = getfilepos(&line, NULL, sv->fileid, sv->chridx-2);
+               note(NULL, "in file included from %s:%d", f, line);
+            }
             memcpy(lx, sv, sizeof *lx);
             free(sv);
             --includedepth;
diff --git a/c/lex.h b/c/lex.h
index 21519f7..20b1bbd 100644
--- a/c/lex.h
+++ b/c/lex.h
@@ -101,7 +101,8 @@ struct lexer {
    bool eof, err;
    struct arena **tmparena;
    bool firstdirective;
-   ushort nppcnd0;
+   short nppcnd0;
+   short inclnerror;
    internstr inclguard;
    uchar chrbuf[1<<10];
    uint chridxbuf[1<<10];
-- 
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