From 446379d2ba196f5070e0838cdf9ca3e10280e532 Mon Sep 17 00:00:00 2001
From: KBS <youdie006@naver.com>
Date: Thu, 10 Sep 2026 15:03:56 +0900
Subject: [PATCH] Throw instead of trapping on modulo by zero (#347)

Op::Modulo was the only arithmetic operator in the switch without a
zero-divisor guard, so {{ a % b }} raised SIGFPE and aborted the host
process. Op::Division already throws at renderer.hpp:307 and
Op::DivisibleBy already checks at :359. Guard the converted divisor,
which is what DivisibleBy does, so a fractional divisor that truncates
to zero is caught too.
---
 include/inja/renderer.hpp    | 6 +++++-
 single_include/inja/inja.hpp | 6 +++++-
 test/test-functions.cpp      | 4 ++++
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/inja/renderer.hpp b/include/inja/renderer.hpp
index 61b6ff0..5174bbe 100644
--- a/include/inja/renderer.hpp
+++ b/include/inja/renderer.hpp
@@ -321,7 +321,11 @@ class Renderer : public NodeVisitor {
     } break;
     case Op::Modulo: {
       const auto args = get_arguments<2>(node);
-      make_result(args[0]->get<const json::number_integer_t>() % args[1]->get<const json::number_integer_t>());
+      const auto divisor = args[1]->get<const json::number_integer_t>();
+      if (divisor == 0) {
+        throw_renderer_error("modulo by zero", node);
+      }
+      make_result(args[0]->get<const json::number_integer_t>() % divisor);
     } break;
     case Op::AtId: {
       const auto container = get_arguments<1, 0, false>(node)[0];
diff --git a/single_include/inja/inja.hpp b/single_include/inja/inja.hpp
index bf18089..1a36521 100644
--- a/single_include/inja/inja.hpp
+++ b/single_include/inja/inja.hpp
@@ -2479,7 +2479,11 @@ class Renderer : public NodeVisitor {
     } break;
     case Op::Modulo: {
       const auto args = get_arguments<2>(node);
-      make_result(args[0]->get<const json::number_integer_t>() % args[1]->get<const json::number_integer_t>());
+      const auto divisor = args[1]->get<const json::number_integer_t>();
+      if (divisor == 0) {
+        throw_renderer_error("modulo by zero", node);
+      }
+      make_result(args[0]->get<const json::number_integer_t>() % divisor);
     } break;
     case Op::AtId: {
       const auto container = get_arguments<1, 0, false>(node)[0];
diff --git a/test/test-functions.cpp b/test/test-functions.cpp
index 4208cfe..aae1dd2 100644
--- a/test/test-functions.cpp
+++ b/test/test-functions.cpp
@@ -36,11 +36,15 @@ TEST_CASE("functions") {
     CHECK(env.render("{{ 1 + 1 * 3 }}", data) == "4");
     CHECK(env.render("{{ (1 + 1) * 3 }}", data) == "6");
     CHECK(env.render("{{ 5 / 2 }}", data) == "2.5");
+    CHECK(env.render("{{ 5 % 2 }}", data) == "1");
+    CHECK(env.render("{{ 7 % -2 }}", data) == "1");
     CHECK(env.render("{{ 5^3 }}", data) == "125");
     CHECK(env.render("{{ 5 + 12 + 4 * (4 - (1 + 1))^2 - 75 * 1 }}", data) == "-42");
 
     CHECK_THROWS_WITH(env.render("{{ +1 }}", data), "[inja.exception.parser_error] (at 1:7) too few arguments");
     CHECK_THROWS_WITH(env.render("{{ 1 + }}", data), "[inja.exception.parser_error] (at 1:8) too few arguments");
+    CHECK_THROWS_WITH(env.render("{{ 5 % 0 }}", data), "[inja.exception.render_error] (at 1:6) modulo by zero");
+    CHECK_THROWS_WITH(env.render("{{ 5 % 0.5 }}", data), "[inja.exception.render_error] (at 1:6) modulo by zero");
   }
 
   SUBCASE("upper") {