Fix bug in scratch_buffer_printf.

c3lang · Apr 9, 2024 · 0473858 · 0473858
1 parent 18b4fce
commit 0473858
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Showing 2 changed files with 4 additions and 3 deletions.
diff --git a/releasenotes.md b/releasenotes.md
@@ -7,7 +7,7 @@
 - Added `print-input` command argument to print all files used for compilation
 
 ### Fixes
-None
+- Incorrect length passed to scratch buffer printf.
 
 ### Stdlib changes
 None

diff --git a/src/utils/stringutils.c b/src/utils/stringutils.c
@@ -353,8 +353,9 @@ void scratch_buffer_printf(const char *format, ...)
 {
 	va_list args;
 	va_start(args, format);
-	uint32_t len_needed = (uint32_t)vsnprintf(&scratch_buffer.str[scratch_buffer.len], MAX_STRING_BUFFER, format, args);
-	if (scratch_buffer.len + len_needed > MAX_STRING_BUFFER - 1)
+	size_t available = MAX_STRING_BUFFER - scratch_buffer.len;
+	uint32_t len_needed = (uint32_t)vsnprintf(&scratch_buffer.str[scratch_buffer.len], available, format, args);
+	if (len_needed > available - 1)
 	{
 		error_exit("Scratch buffer size (%d chars) exceeded", MAX_STRING_BUFFER - 1);
 	}