From 506a608f59dfe16a5e568293583720ab5af3e261 Mon Sep 17 00:00:00 2001
From: mike <mikefc@coolbutuseless.com>
Date: Wed, 1 May 2024 20:33:59 +1000
Subject: [PATCH] fix underflow issue

---
 DESCRIPTION                                           |  2 +-
 NEWS.md                                               |  5 +++++
 src/R-yyjson-parse.c                                  |  8 +++++---
 .../testthat/test-bug44-infinite-loop-on-bad-string.R | 11 +++++++++++
 4 files changed, 22 insertions(+), 4 deletions(-)
 create mode 100644 tests/testthat/test-bug44-infinite-loop-on-bad-string.R

diff --git a/DESCRIPTION b/DESCRIPTION
index 6cffb6d..e48fbab 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: yyjsonr
 Type: Package
 Title: Fast 'JSON', 'NDJSON' and 'GeoJSON' Parser and Generator 
-Version: 0.1.20.9000
+Version: 0.1.20.9001
 Authors@R: c(
     person("Mike", "Cheng", role = c("aut", "cre", 'cph'), 
     email = "mikefc@coolbutuseless.com"),
diff --git a/NEWS.md b/NEWS.md
index c4a9f91..ce109d0 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,4 +1,9 @@
 
+
+# yyjsonr 0.1.20.9001 2024-05-01
+
+* Fix underflow issue when trying to verbosely report an error at position 0
+
 # yyjsonr 0.1.20.9000 2024-04-12
 
 * Get size of gzipped file in an endian-neutral way. Issue #39
diff --git a/src/R-yyjson-parse.c b/src/R-yyjson-parse.c
index e17e3e3..dda4392 100644
--- a/src/R-yyjson-parse.c
+++ b/src/R-yyjson-parse.c
@@ -1820,9 +1820,11 @@ void output_verbose_error(const char *str, yyjson_read_err err) {
   
   // Print a "^" to point to the error
   size_t pos = ERR_CONTEXT;
-  pos = err.pos < ERR_CONTEXT ? err.pos - 1 : ERR_CONTEXT;
-  for (unsigned int i = 0; i < pos; i++) {
-    Rprintf(" ");
+  if (err.pos > 0) {
+    pos = err.pos < ERR_CONTEXT ? err.pos - 1 : ERR_CONTEXT;
+    for (unsigned int i = 0; i < pos; i++) {
+      Rprintf(" ");
+    }
   }
   Rprintf("^\n");
 }
diff --git a/tests/testthat/test-bug44-infinite-loop-on-bad-string.R b/tests/testthat/test-bug44-infinite-loop-on-bad-string.R
new file mode 100644
index 0000000..17fff79
--- /dev/null
+++ b/tests/testthat/test-bug44-infinite-loop-on-bad-string.R
@@ -0,0 +1,11 @@
+
+
+test_that("Invalid string input should cause error", {
+  
+  testthat::capture_output({
+  expect_error({
+    read_json_str("hello")
+  })
+  })
+  
+})