tree-wide: fix a pile of lints

This:
- Converts a bunch of C style casts into C++ casts.
- Removes some very silly pointer subtraction code (which is no more or
  less busted on i686 than it began)
- Fixes some "technically UB" that never had to be UB in the first
  place.
- Makes finally follow the noexcept status of the inner function. Maybe
  in the future we should ban the function from not being noexcept, but
  that is not today.
- Makes various locally-used exceptions inherit from std::exception.

Change-Id: I22e66972602604989b5e494fd940b93e0e6e9297

4 files changed, 10 insertions, 6 deletions

diff --git a/tests/unit/libstore/filetransfer.cc b/tests/unit/libstore/filetransfer.cc
index 6e8cf3bbe..71e7392fc 100644
--- a/tests/unit/libstore/filetransfer.cc
+++ b/tests/unit/libstore/filetransfer.cc
@@ -6,7 +6,6 @@
 #include <future>
 #include <gtest/gtest.h>
 #include <netinet/in.h>
-#include <stdexcept>
 #include <string>
 #include <string_view>
 #include <sys/poll.h>
@@ -130,7 +129,7 @@ serveHTTP(std::string status, std::string headers, std::function<std::string()>
 
 TEST(FileTransfer, exceptionAbortsDownload)
 {
-    struct Done
+    struct Done : std::exception
     {};
 
     auto ft = makeFileTransfer();
diff --git a/tests/unit/libutil/closure.cc b/tests/unit/libutil/closure.cc
index b4eaad6f9..8cac9a9fd 100644
--- a/tests/unit/libutil/closure.cc
+++ b/tests/unit/libutil/closure.cc
@@ -28,7 +28,7 @@ TEST(closure, correctClosure) {
 }
 
 TEST(closure, properlyHandlesDirectExceptions) {
-    struct TestExn {};
+    struct TestExn : std::exception {};
     EXPECT_THROW(
         computeClosure<string>(
             {"A"},
diff --git a/tests/unit/libutil/generator.cc b/tests/unit/libutil/generator.cc
index 800e6ca8a..22cc085f9 100644
--- a/tests/unit/libutil/generator.cc
+++ b/tests/unit/libutil/generator.cc
@@ -85,6 +85,7 @@ TEST(Generator, nestsExceptions)
         co_yield 1;
         co_yield []() -> Generator<int> {
             co_yield 9;
+            // NOLINTNEXTLINE(hicpp-exception-baseclass)
             throw 1;
             co_yield 10;
         }();
@@ -101,6 +102,7 @@ TEST(Generator, exception)
     {
         auto g = []() -> Generator<int> {
             co_yield 1;
+            // NOLINTNEXTLINE(hicpp-exception-baseclass)
             throw 1;
         }();
 
@@ -110,6 +112,7 @@ TEST(Generator, exception)
     }
     {
         auto g = []() -> Generator<int> {
+            // NOLINTNEXTLINE(hicpp-exception-baseclass)
             throw 1;
             co_return;
         }();
@@ -173,11 +176,13 @@ struct ThrowTransform
 
     int operator()(bool)
     {
+        // NOLINTNEXTLINE(hicpp-exception-baseclass)
         throw 2;
     }
 
     Generator<int, void> operator()(Generator<int> && inner)
     {
+        // NOLINTNEXTLINE(hicpp-exception-baseclass)
         throw false;
     }
 };
diff --git a/tests/unit/libutil/tests.cc b/tests/unit/libutil/tests.cc
index 9a44ad59b..29a5f7164 100644
--- a/tests/unit/libutil/tests.cc
+++ b/tests/unit/libutil/tests.cc
@@ -29,12 +29,12 @@ namespace nix {
         char cwd[PATH_MAX+1];
         auto p = absPath("");
 
-        ASSERT_EQ(p, getcwd((char*)&cwd, PATH_MAX));
+        ASSERT_EQ(p, getcwd(cwd, PATH_MAX));
     }
 
     TEST(absPath, usesOptionalBasePathWhenGiven) {
         char _cwd[PATH_MAX+1];
-        char* cwd = getcwd((char*)&_cwd, PATH_MAX);
+        char* cwd = getcwd(_cwd, PATH_MAX);
 
         auto p = absPath("", cwd);
 
@@ -43,7 +43,7 @@ namespace nix {
 
     TEST(absPath, isIdempotent) {
         char _cwd[PATH_MAX+1];
-        char* cwd = getcwd((char*)&_cwd, PATH_MAX);
+        char* cwd = getcwd(_cwd, PATH_MAX);
         auto p1 = absPath(cwd);
         auto p2 = absPath(p1);