chore: avoid silent implicit type conversions

CMakeLists.txt

@@ -136,6 +136,36 @@ include(GoogleTest)
 include_directories(include)
 include_directories(src)
 
+# Stricter implicit-conversion warnings for first-party code only. Placed after
+# all contrib add_subdirectory() calls so third-party sources (librseq,
+# libbacktrace, liburing, etc.) keep compiling under their own assumptions;
+# add_compile_options only affects targets created later in this scope. Catches
+# silent value-altering conversions: integer narrowing (uint64_t -> uint32_t),
+# float-to-int truncation, and float-precision loss.
+# None of these are enabled by -Wall/-Wextra.
+# Third-party headers we include (e.g. liburing) are marked SYSTEM so their
+# inline functions do not trip these here.
+add_compile_options(
+    # Integer narrowing. Already includes the -Wshorten-64-to-32 subgroup, so
+    # that 64->32 flag would be redundant here.
+    -Wimplicit-int-conversion
+
+    # float/double -> int truncation.
+    -Wfloat-conversion
+
+    # double -> float narrowing, and int -> float precision loss
+    # (-Wimplicit-float-conversion includes the -Wimplicit-int-float-conversion
+    # subgroup). Also bit noisy
+    # -Wimplicit-float-conversion
+
+    # Signed <-> unsigned changes. Correct in principle but very noisy on
+    # existing code; enable once the tree is clean.
+    # -Wsign-conversion
+
+    # This catches all types of implicit conversations. But currently too noisy
+    # -Wconversion
+)
+
 add_subdirectory(src/util)
 add_subdirectory(src/fibers)
 add_subdirectory(src/gdb)

contrib/liburing-cmake/CMakeLists.txt

@@ -77,7 +77,7 @@ add_library(liburing STATIC
 
 # LIBURING_BIN must come before LIBURING_SRC/src/include so the generated
 # liburing/compat.h and liburing/io_uring_version.h shadow the absent originals.
-target_include_directories(liburing PUBLIC ${LIBURING_BIN} ${LIBURING_SRC}/src/include)
+target_include_directories(liburing SYSTEM PUBLIC ${LIBURING_BIN} ${LIBURING_SRC}/src/include)
 
 target_compile_definitions(liburing PRIVATE
     _GNU_SOURCE

src/fibers/cpu.cpp

@@ -36,7 +36,7 @@ static int readSysfsUint32(const char * path, uint32_t * out) noexcept
     buf[n] = '\0';
 
     char * end;
-    uint32_t val = ::strtoul(buf, &end, 10);
+    uint32_t val = static_cast<uint32_t>(::strtoul(buf, &end, 10));
     if (end == buf)
     {
         return EINVAL;

src/fibers/fiber.cpp

@@ -637,7 +637,7 @@ struct FiberScheduler::ProcessorState
 void FiberScheduler::ProcessorState::initialize(uint32_t cpu) noexcept
 {
     SILK_ASSERT(cpu < INVALID_PROCESSOR_NUMBER);
-    number = cpu;
+    number = static_cast<uint16_t>(cpu);
 
     readyQueue.initialize(options.readyQueueCapacity);
 
@@ -1041,7 +1041,7 @@ void FiberScheduler::initialize(const Options * userOptions) noexcept
         if (CPU_ISSET(cpu, &processCpuSet))
         {
             ProcessorState * processor = &scheduler->processorState[cpu];
-            processor->number = cpu;
+            processor->number = static_cast<uint16_t>(cpu);
         }
     }
 
@@ -1266,7 +1266,7 @@ void FiberScheduler::enqueueReady(Fiber * fiber) noexcept
         {
             if (fiber->processorNumber == INVALID_PROCESSOR_NUMBER)
             {
-                fiber->processorNumber = getCurrentProcessor();
+                fiber->processorNumber = static_cast<uint16_t>(getCurrentProcessor());
             }
 
             ProcessorState * processor = &scheduler->processorState[fiber->processorNumber];

src/util/benchmarks/bounded-queue-bench.cpp

@@ -38,7 +38,7 @@ class BoundedQueueBench : public benchmark::Fixture
         {
             for (uint64_t i = 0; i < CAPACITY; ++i)
             {
-                bool b = queue.enqueue(i);
+                bool b = queue.enqueue(static_cast<int>(i));
                 SILK_ASSERT(b);
             }
         }