usrsctp: make unused-but-set-variable non-fatal for gcc 16

since usrsctp builds with -Werror by default, and gcc 16's unused
variable analysis is better than previous versions, this causes a build
failure. a fix for this particular variable has been submitted upstream,
but this is sufficient in the interim.

doc/release-notes/rl-2611.section.md

@@ -16,6 +16,8 @@
   +nixpkgs.url = "https://channels.nixos.org/nixos-26.05/nixexprs.tar.zst";
   ```
 
+- GCC has been updated from GCC 15 to GCC 16. This introduces some backwards-incompatible changes. Refer to the [upstream porting guide](https://gcc.gnu.org/gcc-16/porting_to.html) for details.
+
 ## Backward Incompatibilities {#sec-nixpkgs-release-26.11-incompatibilities}
 
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->

pkgs/by-name/je/jemalloc/package.nix

@@ -2,6 +2,7 @@
   lib,
   stdenv,
   fetchFromGitHub,
+  fetchpatch,
   autoreconfHook,
   # By default, jemalloc puts a je_ prefix onto all its symbols on OSX, which
   # then stops downstream builds (mariadb in particular) from detecting it. This
@@ -59,6 +60,16 @@ stdenv.mkDerivation (finalAttrs: {
     # A (longer) patch addressing the failure posted upstream at:
     # https://github.com/jemalloc/jemalloc/pull/2954
     ./skip-extent-test-with-prof-active.patch
+
+    # the nonstandard `std::__throw_bad_alloc` is no longer exposed in gcc 16.
+    # this makes it conditional on exceptions and defers to either
+    # `throw std::bad_alloc()` or `std::terminate` as appropriate.
+    # https://github.com/jemalloc/jemalloc/pull/2900
+    (fetchpatch {
+      name = "jemalloc-dont-use-nonstandard-throw-bad-alloc.patch";
+      url = "https://github.com/jemalloc/jemalloc/commit/1a15fe33a48c52bfe26ea83e49f0d317a47da3ea.patch";
+      hash = "sha256-pL9fo8UMSbFlHCo3LFFkw0qBsdrVHcEJIkLutZYa2Yg=";
+    })
   ];
 
   nativeBuildInputs = [

pkgs/by-name/so/sourceHighlight/gcc16-disambiguate-regex-ranges-test.patch

@@ -0,0 +1,57 @@
+diff --git a/lib/tests/test_regexranges_main.cpp b/lib/tests/test_regexranges_main.cpp
+index 567d79230c..e28bba47e5 100644
+--- a/lib/tests/test_regexranges_main.cpp
++++ b/lib/tests/test_regexranges_main.cpp
+@@ -12,26 +12,26 @@
+ using namespace std;
+ using namespace srchilite;
+ 
+-RegexRanges ranges;
++RegexRanges regexRanges;
+ 
+ void check_range_regex(const string &s, bool expectedTrue = true) {
+     cout << "checking " << s << endl;
+     if (expectedTrue)
+-        assertTrue(ranges.addRegexRange(s));
++        assertTrue(regexRanges.addRegexRange(s));
+     else
+-        assertFalse(ranges.addRegexRange(s));
++        assertFalse(regexRanges.addRegexRange(s));
+ }
+ 
+ void check_match(const string &line, const string &expected = "") {
+     cout << "searching inside " << line;
+     const boost::regex *matched = 0;
+     if (expected != "") {
+-        matched = ranges.matches(line);
++        matched = regexRanges.matches(line);
+         assertTrue(matched != 0);
+         assertEquals(expected, matched->str());
+         cout << " found " << *matched << endl;
+     } else {
+-        assertTrue(ranges.matches(line) == 0);
++        assertTrue(regexRanges.matches(line) == 0);
+         cout << " not found" << endl;
+     }
+ }
+@@ -39,9 +39,9 @@
+ void check_in_range(const string &s, bool expectedTrue = true) {
+     cout << "checking " << s << "... ";
+     if (expectedTrue) {
+-        assertTrue(ranges.isInRange(s));
++        assertTrue(regexRanges.isInRange(s));
+     } else {
+-        assertFalse(ranges.isInRange(s));
++        assertFalse(regexRanges.isInRange(s));
+     }
+     cout << expectedTrue << endl;
+ }
+@@ -57,7 +57,7 @@
+     check_range_regex("{notclosed");
+ 
+     // reset regular expressions
+-    ranges.clear();
++    regexRanges.clear();
+ 
+     check_range_regex("/// foo");
+     check_range_regex("/// bar");

pkgs/by-name/so/sourceHighlight/package.nix

@@ -37,6 +37,11 @@ stdenv.mkDerivation rec {
       url = "https://git.savannah.gnu.org/cgit/src-highlite.git/patch/?id=ab9fe5cb9b85c5afab94f2a7f4b6d7d473c14ee9";
       hash = "sha256-wmSLgLnLuFE+IC6AjxzZp/HEnaOCS1VfY2cac0T7Y+w=";
     })
+
+    # GCC 16 detects ambiguity in the `ranges` name in a test (conflicts with
+    # `namespace std::range { }` from GCC), so we rename the variable to
+    # disambiguate.
+    ./gcc16-disambiguate-regex-ranges-test.patch
   ]
   ++ lib.optionals stdenv.cc.isClang [
     # Adds compatibility with C++17 by removing the `register` storage class specifier.

pkgs/by-name/us/usrsctp/package.nix

@@ -38,6 +38,11 @@ stdenv.mkDerivation (finalAttrs: {
 
   nativeBuildInputs = [ cmake ];
 
+  # GCC 16's unused variable analysis is more advanced, leading to a build
+  # failure since usrsctp builds with -Wno-error.
+  # https://github.com/sctplab/usrsctp/pull/744
+  cmakeFlags = [ (lib.cmakeFeature "CMAKE_C_FLAGS" "-Wno-error=unused-but-set-variable") ];
+
   # https://github.com/sctplab/usrsctp/issues/662
   postPatch = ''
     substituteInPlace usrsctplib/CMakeLists.txt \

pkgs/os-specific/linux/minimal-bootstrap/gcc/glibc.nix

@@ -22,7 +22,7 @@
 }:
 let
   pname = "gcc";
-  version = "15.3.0";
+  version = "16.1.0";
   linkerName =
     {
       i686-linux = "ld-linux.so.2";
@@ -32,7 +32,7 @@ let
 
   src = fetchurl {
     url = "mirror://gnu/gcc/gcc-${version}/gcc-${version}.tar.xz";
-    hash = "sha256-+lnBvu+JlfJ8TXHB3yJ1hxiTFdPm+v8btDBuYbDFMOs=";
+    hash = "sha256-UO+02Uwzl6/zsNYaWr10i03THZ0/Kre+BbFx02pRD3k=";
   };
 
   gmpVersion = "6.3.0";

pkgs/os-specific/linux/minimal-bootstrap/gcc/latest.nix

@@ -21,11 +21,11 @@
 }:
 let
   pname = "gcc";
-  version = "15.3.0";
+  version = "16.1.0";
 
   src = fetchurl {
     url = "mirror://gnu/gcc/gcc-${version}/gcc-${version}.tar.xz";
-    hash = "sha256-+lnBvu+JlfJ8TXHB3yJ1hxiTFdPm+v8btDBuYbDFMOs=";
+    hash = "sha256-UO+02Uwzl6/zsNYaWr10i03THZ0/Kre+BbFx02pRD3k=";
   };
 
   gmpVersion = "6.3.0";

pkgs/top-level/all-packages.nix

@@ -3266,7 +3266,7 @@ with pkgs;
   gerbilPackages-unstable = pkgs.gerbil-support.gerbilPackages-unstable; # NB: don't recurseIntoAttrs for (unstable!) libraries
   glow-lang = pkgs.gerbilPackages-unstable.glow-lang;
 
-  default-gcc-version = 15;
+  default-gcc-version = 16;
   gcc = pkgs.${"gcc${toString default-gcc-version}"};
   gccFun = callPackage ../development/compilers/gcc;
   gcc-unwrapped = gcc.cc;