From 1dd19e56fb81d1334bb21e4aa097f9593576feb7 Mon Sep 17 00:00:00 2001
From: lemon <lsof@mailbox.org>
Date: Sat, 6 Aug 2022 07:07:26 +0200
Subject: print source on error

---
 bootstrap/util.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 48 insertions(+), 1 deletion(-)

(limited to 'bootstrap/util.c')

diff --git a/bootstrap/util.c b/bootstrap/util.c
index be3aea0..c9be845 100644
--- a/bootstrap/util.c
+++ b/bootstrap/util.c
@@ -16,6 +16,7 @@ jkhash(u32 h, const u8 *data, size_t length) {
 }
 
 static const char *filepaths[100];
+static const char *filemmaps[100];
 static int nfilepaths = 0;
 
 int addfilepath(const char *s) {
@@ -81,6 +82,50 @@ xstrdup(const char *s) {
    return strcpy(xmalloc(strlen(s) + 1), s);
 }
 
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+static void
+eprifileline(struct span span) {
+   const char *src = filemmaps[span.fileid];
+   long i, j ,n;
+   if (!src) {
+      const char *path = fileid2path(span.fileid);
+      struct stat st;
+      int fd = open(path, O_RDONLY);
+      if (fd < -1) {
+         perror("open()");
+         return;
+      }
+      if (stat(path, &st) < 0) {
+         perror("stat()");
+         close(fd);
+         return;
+      }
+      filemmaps[span.fileid] = src = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+      assert(src && src != (void *)-1 && "mmap");
+      close(fd);
+   }
+   // line begin
+   for (i = span.idx; i > 0 && src[i] != '\n'; --i) ;
+   ++i;
+
+   // line end
+   for (j = span.idx; src[j] && src[j] != '\n'; ++j) ;
+   --j;
+
+   n = fprintf(stderr, "%4d| ", span.line);
+   for (long k = i; k < j; ++k)
+      epri("%c", src[k]);
+   epri("\n");
+   while (n--)
+      epri(" ");
+   for (int k = 0; src[k] && src[k] != '\n'; ++k)
+      fprintf(stderr, "%s", k + 1 == span.col ? "^" : " ");
+   epri("\n");
+}
 
 void noreturn
 fatal(struct parser *P, struct span span, const char *fmt, ...) {
@@ -91,12 +136,14 @@ fatal(struct parser *P, struct span span, const char *fmt, ...) {
    epri("%s:%d:%d: error: ", fileid2path(span.fileid), span.line, span.col);
    vepri(fmt, ap);
    epri("\n");
+   eprifileline(span);
    for (struct expan *ep = P->curexpan; ep; ep = ep->prev, ++i) {
       if (ep->name && (i < 8 || !ep->prev || !ep->prev->prev)) {
          span = ep->span;
-         epri("    while expanding macro `%s' at %s:%d:%d\n",
+         epri("* while expanding macro `%s' at %s:%d:%d\n",
                ep->name,
                fileid2path(ep->span.fileid), span.line, span.col);
+         eprifileline(span);
       } else if (ep->name && i == 10) {
          epri("    ... (some expansions omitted)\n");
       }
-- 
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