From 566b2d14043a439ed83cd02774af44f225ecad72 Mon Sep 17 00:00:00 2001
From: SamareshSingh <97642706+ssam18@users.noreply.github.com>
Date: Mon, 9 Feb 2026 13:58:20 -0600
Subject: [PATCH] Fix #3525: Make level name matching case-insensitive (#3535)

Modified from_str() to perform case-insensitive comparison for all level names.
This allows environment variables and SPDLOG_LEVEL_NAMES to use uppercase or
mixed case level names (e.g., DEBUG, INFO, Warning) while maintaining full
backward compatibility with existing lowercase names.
---
 include/spdlog/common-inl.h | 22 +++++++++++++++++++---
 tests/test_cfg.cpp          | 30 ++++++++++++++++++++++++++++++
 tests/test_misc.cpp         | 11 +++++++++++
 3 files changed, 60 insertions(+), 3 deletions(-)

diff --git a/include/spdlog/common-inl.h b/include/spdlog/common-inl.h
index f35901c5..77064756 100644
--- a/include/spdlog/common-inl.h
+++ b/include/spdlog/common-inl.h
@@ -29,15 +29,31 @@ SPDLOG_INLINE const char *to_short_c_str(spdlog::level::level_enum l) SPDLOG_NOE
 }
 
 SPDLOG_INLINE spdlog::level::level_enum from_str(const std::string &name) SPDLOG_NOEXCEPT {
-    auto it = std::find(std::begin(level_string_views), std::end(level_string_views), name);
+    auto it = std::find_if(std::begin(level_string_views), std::end(level_string_views),
+                           [&name](const string_view_t &level_name) {
+                               return level_name.size() == name.size() &&
+                                      std::equal(name.begin(), name.end(), level_name.begin(),
+                                                 [](char a, char b) {
+                                                     return std::tolower(static_cast<unsigned char>(a)) ==
+                                                            std::tolower(static_cast<unsigned char>(b));
+                                                 });
+                           });
     if (it != std::end(level_string_views))
         return static_cast<level::level_enum>(std::distance(std::begin(level_string_views), it));
 
     // check also for "warn" and "err" before giving up..
-    if (name == "warn") {
+    auto iequals = [](const std::string &a, const std::string &b) {
+        return a.size() == b.size() &&
+               std::equal(a.begin(), a.end(), b.begin(), [](char ac, char bc) {
+                   return std::tolower(static_cast<unsigned char>(ac)) ==
+                          std::tolower(static_cast<unsigned char>(bc));
+               });
+    };
+
+    if (iequals(name, "warn")) {
         return level::warn;
     }
-    if (name == "err") {
+    if (iequals(name, "err")) {
         return level::err;
     }
     return level::off;
diff --git a/tests/test_cfg.cpp b/tests/test_cfg.cpp
index 7dec94b4..cff35d33 100644
--- a/tests/test_cfg.cpp
+++ b/tests/test_cfg.cpp
@@ -176,3 +176,33 @@ TEST_CASE("restore-to-default", "[cfg]") {
     load_argv_levels(2, argv);
     REQUIRE(spdlog::default_logger()->level() == spdlog::level::info);
 }
+
+TEST_CASE("uppercase-level-names", "[cfg]") {
+    spdlog::drop("l1");
+    spdlog::drop("l2");
+    
+#ifdef CATCH_PLATFORM_WINDOWS
+    _putenv_s("SPDLOG_LEVEL", "l1=DEBUG,INFO");
+#else
+    setenv("SPDLOG_LEVEL", "l1=DEBUG,INFO", 1);
+#endif
+    load_env_levels();
+    auto l1 = spdlog::create<test_sink_st>("l1");
+    auto l2 = spdlog::create<test_sink_st>("l2");
+    
+    REQUIRE(l1->level() == spdlog::level::debug);
+    REQUIRE(l2->level() == spdlog::level::info);
+    REQUIRE(spdlog::default_logger()->level() == spdlog::level::info);
+    
+    // Test with argv
+    spdlog::drop("l3");
+    const char *argv[] = {"ignore", "SPDLOG_LEVEL=l3=WARN,ERROR"};
+    load_argv_levels(2, argv);
+    auto l3 = spdlog::create<test_sink_st>("l3");
+    
+    REQUIRE(l3->level() == spdlog::level::warn);
+    REQUIRE(spdlog::default_logger()->level() == spdlog::level::err);
+    
+    // Reset to info
+    spdlog::set_level(spdlog::level::info);
+}
diff --git a/tests/test_misc.cpp b/tests/test_misc.cpp
index ff32fed2..e855e1b2 100644
--- a/tests/test_misc.cpp
+++ b/tests/test_misc.cpp
@@ -73,6 +73,17 @@ TEST_CASE("to_level_enum", "[convert_to_level_enum]") {
     REQUIRE(spdlog::level::from_str("critical") == spdlog::level::critical);
     REQUIRE(spdlog::level::from_str("off") == spdlog::level::off);
     REQUIRE(spdlog::level::from_str("null") == spdlog::level::off);
+    REQUIRE(spdlog::level::from_str("TRACE") == spdlog::level::trace);
+    REQUIRE(spdlog::level::from_str("DEBUG") == spdlog::level::debug);
+    REQUIRE(spdlog::level::from_str("INFO") == spdlog::level::info);
+    REQUIRE(spdlog::level::from_str("WARNING") == spdlog::level::warn);
+    REQUIRE(spdlog::level::from_str("WARN") == spdlog::level::warn);
+    REQUIRE(spdlog::level::from_str("ERROR") == spdlog::level::err);
+    REQUIRE(spdlog::level::from_str("ERR") == spdlog::level::err);
+    REQUIRE(spdlog::level::from_str("CRITICAL") == spdlog::level::critical);
+    REQUIRE(spdlog::level::from_str("OFF") == spdlog::level::off);
+    REQUIRE(spdlog::level::from_str("TrAcE") == spdlog::level::trace);
+    REQUIRE(spdlog::level::from_str("DeBuG") == spdlog::level::debug);
 }
 
 TEST_CASE("periodic flush", "[periodic_flush]") {