From c714caa27aba5c838faca1509f41f98311073f47 Mon Sep 17 00:00:00 2001
From: Martin Griffin <martinrgriffin@gmail.com>
Date: Wed, 4 Dec 2024 18:22:35 +0000
Subject: [PATCH] trainerproc: Fix showing incorrect error context (#5769)

---
 tools/trainerproc/main.c | 98 ++++++++++++++++++++++------------------
 1 file changed, 53 insertions(+), 45 deletions(-)

diff --git a/tools/trainerproc/main.c b/tools/trainerproc/main.c
index 8b939a955f..f1bcf1bfa4 100644
--- a/tools/trainerproc/main.c
+++ b/tools/trainerproc/main.c
@@ -251,51 +251,6 @@ static bool set_parse_error(struct Parser *p, struct SourceLocation location, co
     return false;
 }
 
-static bool show_parse_error(struct Parser *p)
-{
-    // Print error message.
-    int n = fprintf(stderr, "%s:%d: ", p->source->path, p->error_location.line);
-    fprintf(stderr, "error: %s\n", p->error);
-
-    // Seek to the line.
-    int line, begin, end;
-    for (line = 1, begin = 0; begin < p->source->buffer_n; begin++)
-    {
-        if (p->error_location.line == line)
-            break;
-        if (p->source->buffer[begin] == '\n')
-            line++;
-    }
-    for (end = begin; end < p->source->buffer_n; end++)
-    {
-        if (p->source->buffer[end] == '\n')
-            break;
-    }
-
-    // Print the source line.
-    fprintf(stderr, "%s:%d: %.*s\n", p->source->path, p->error_location.line, end - begin, &p->source->buffer[begin]);
-
-    // Print caret pointing at the column.
-    fprintf(stderr, "%*s", n, "");
-    for (int column = 1; column < p->error_location.column && begin + column < end; column++)
-    {
-        unsigned char c = p->source->buffer[begin + column];
-        fputc(c == '\t' ? c : ' ', stderr);
-    }
-    fprintf(stderr, "^\n");
-
-    p->error = NULL;
-    p->fatal_error = true;
-
-    return false;
-}
-
-static bool set_show_parse_error(struct Parser *p, struct SourceLocation location, const char *error)
-{
-    set_parse_error(p, location, error);
-    return show_parse_error(p);
-}
-
 __attribute__((warn_unused_result))
 static bool peek_char(struct Parser *p, unsigned char *c)
 {
@@ -618,6 +573,59 @@ static bool match_move_identifier(struct Parser *p, struct Token *t)
     return true;
 }
 
+static bool show_parse_error(struct Parser *p)
+{
+    // Print error message.
+    int n = fprintf(stderr, "%s:%d: ", p->source->path, p->error_location.line);
+    fprintf(stderr, "error: %s\n", p->error);
+
+    struct Parser p_ = {
+        .source = p->source,
+        .location = { .line = 1, .column = 1 },
+        .offset = 0,
+    };
+
+    for (;;) {
+        if (p->error_location.line == p_.location.line)
+            break;
+        if (!match_empty_line(&p_))
+            skip_line(&p_);
+        if (match_eof(&p_))
+            assert(false);
+    }
+
+    int begin = p_.offset;
+    int end;
+    for (end = begin; end < p->source->buffer_n; end++)
+    {
+        if (p->source->buffer[end] == '\n')
+            break;
+    }
+
+    // Print the source line.
+    fprintf(stderr, "%s:%d: %.*s\n", p->source->path, p->error_location.line, end - begin, &p->source->buffer[begin]);
+
+    // Print caret pointing at the column.
+    fprintf(stderr, "%*s", n, "");
+    for (int column = 1; column < p->error_location.column && begin + column < end; column++)
+    {
+        unsigned char c = p->source->buffer[begin + column];
+        fputc(c == '\t' ? c : ' ', stderr);
+    }
+    fprintf(stderr, "^\n");
+
+    p->error = NULL;
+    p->fatal_error = true;
+
+    return false;
+}
+
+static bool set_show_parse_error(struct Parser *p, struct SourceLocation location, const char *error)
+{
+    set_parse_error(p, location, error);
+    return show_parse_error(p);
+}
+
 __attribute__((warn_unused_result))
 static bool parse_section(struct Parser *p, struct Token *section)
 {