fix out-of-bounds read in basic_format_args::get

The lint workflow was path-filtered to source files, so PRs that didn't
touch them never ran clang-format/cmake-format. Since those checks are
required, such PRs were blocked forever waiting for a status that never
came. Drop the paths filter so the workflow always reports a status.

.github/workflows/lint.yml

@@ -2,11 +2,6 @@ name: lint
 
 on:
   pull_request:
-    paths:
-      - '**.h'
-      - '**.cc'
-      - '**.cmake'
-      - '**/CMakeLists.txt'
 
 permissions:
   contents: read

.github/workflows/release.yml

@@ -87,7 +87,10 @@ jobs:
     permissions:
       actions: read
       id-token: write
-      contents: read
+      # contents: write is required because the generator's (skipped)
+      # upload-assets job declares it, and a reusable workflow's job
+      # permissions may not exceed the caller's, or the run fails at startup.
+      contents: write
     uses: slsa-framework/slsa-github-generator/.github/workflows/generator_generic_slsa3.yml@v2.1.0
     with:
       base64-subjects: ${{ needs.build.outputs.hashes }}

include/fmt/base.h

@@ -2593,7 +2593,7 @@ template <typename Context> class basic_format_args {
   FMT_CONSTEXPR auto get(int id) const -> format_arg {
     auto arg = format_arg();
     if (!is_packed()) {
-      if (id < max_size()) arg = args_[id];
+      if (unsigned(id) < unsigned(max_size())) arg = args_[id];
       return arg;
     }
     if (unsigned(id) >= detail::max_packed_args) return arg;

test/printf-test.cc

@@ -116,6 +116,17 @@ TEST(printf_test, invalid_arg_index) {
                    "argument not found");
 }
 
+TEST(printf_test, zero_positional_width_precision) {
+  // A '0' positional index for a '*' width or precision must be rejected. Use
+  // enough arguments to exercise the unpacked argument storage path.
+  EXPECT_THROW_MSG(test_sprintf("%*0$d", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
+                                13, 14, 15, 16),
+                   format_error, "argument not found");
+  EXPECT_THROW_MSG(test_sprintf("%.*0$d", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
+                                13, 14, 15, 16),
+                   format_error, "argument not found");
+}
+
 TEST(printf_test, default_align_right) {
   EXPECT_PRINTF("   42", "%5d", 42);
   EXPECT_PRINTF("  abc", "%5s", "abc");