diff --git a/format.cc b/format.cc
index 0a839223..bcb660a9 100644
--- a/format.cc
+++ b/format.cc
@@ -109,6 +109,12 @@ inline int safe_printf(char *buffer, size_t size, const char *format, ...) {
 
 #endif  // _MSC_VER
 
+template <typename T>
+struct IsLongDouble { enum {VALUE = 0}; };
+
+template <>
+struct IsLongDouble<long double> { enum {VALUE = 1}; };
+
 const char RESET_COLOR[] = "\x1b[0m";
 
 typedef void (*FormatFunc)(fmt::Writer &, int , fmt::StringRef);
@@ -260,8 +266,6 @@ inline Arg::StringValue<wchar_t> ignore_incompatible_str(
     Arg::StringValue<wchar_t> s) { return s; }
 }  // namespace
 
-int fmt::internal::signbit_noinline(double value) { return getsign(value); }
-
 void fmt::SystemError::init(
     int error_code, StringRef format_str, const ArgList &args) {
   error_code_ = error_code;
@@ -645,7 +649,7 @@ void fmt::BasicWriter<Char>::write_double(T value, const FormatSpec &spec) {
     *format_ptr++ = '.';
     *format_ptr++ = '*';
   }
-  if (internal::IsLongDouble<T>::VALUE)
+  if (IsLongDouble<T>::VALUE)
     *format_ptr++ = 'L';
   *format_ptr++ = type;
   *format_ptr = '\0';
diff --git a/format.h b/format.h
index 9a2f75c6..8d251a63 100644
--- a/format.h
+++ b/format.h
@@ -410,8 +410,6 @@ inline bool is_negative(T value) {
   return SignChecker<std::numeric_limits<T>::is_signed>::is_negative(value);
 }
 
-int signbit_noinline(double value);
-
 template <typename T>
 struct IntTraits {
   // Smallest of uint32_t and uint64_t that is large enough to represent
@@ -435,12 +433,6 @@ FMT_SPECIALIZE_MAKE_UNSIGNED(int, unsigned);
 FMT_SPECIALIZE_MAKE_UNSIGNED(long, unsigned long);
 FMT_SPECIALIZE_MAKE_UNSIGNED(LongLong, ULongLong);
 
-template <typename T>
-struct IsLongDouble { enum {VALUE = 0}; };
-
-template <>
-struct IsLongDouble<long double> { enum {VALUE = 1}; };
-
 void report_unknown_type(char code, const char *type);
 
 extern const uint32_t POWERS_OF_10_32[];
@@ -452,7 +444,7 @@ extern const uint64_t POWERS_OF_10_64[];
 inline unsigned count_digits(uint64_t n) {
   // Based on http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
   // and the benchmark https://github.com/localvoid/cxx-benchmark-count-digits.
-  uint64_t t = (64 - __builtin_clzll(n | 1)) * 1233 >> 12;
+  unsigned t = (64 - __builtin_clzll(n | 1)) * 1233 >> 12;
   return t - (n < POWERS_OF_10_64[t]) + 1;
 }
 # if FMT_GCC_VERSION >= 400 || FMT_HAS_BUILTIN(__builtin_clz)
@@ -1862,10 +1854,10 @@ class FormatInt {
   }
 
   void FormatSigned(LongLong value) {
-    ULongLong abs_value = value;
+    ULongLong abs_value = static_cast<ULongLong>(value);
     bool negative = value < 0;
     if (negative)
-      abs_value = 0 - value;
+      abs_value = 0 - abs_value;
     str_ = format_decimal(abs_value);
     if (negative)
       *--str_ = '-';
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 31b1e455..f30ca70a 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -1,17 +1,21 @@
 set(TEST_MAIN_SRC test-main.cc gtest-extra.cc gtest-extra.h util.cc)
 add_library(test-main ${TEST_MAIN_SRC})
-target_link_libraries(test-main gtest format)
+target_link_libraries(test-main gtest)
 
 # Adds a test.
 # Usage: add_fmt_test(name libs srcs...)
 function(add_fmt_test name libs)
-  add_executable(${name} ${name}.cc ${ARGN})
+  cmake_parse_arguments(add_fmt_test CUSTOM_LINK "" "" ${ARGN})
+  add_executable(${name} ${name}.cc ${add_fmt_test_UNPARSED_ARGUMENTS})
   target_link_libraries(${name} ${libs})
+  if (NOT add_fmt_test_CUSTOM_LINK)
+    target_link_libraries(${name} format)
+  endif ()
   add_test(${name} ${name})
 endfunction()
 
 add_fmt_test(gtest-extra-test test-main)
-add_fmt_test(format-test test-main)
+add_fmt_test(format-test test-main CUSTOM_LINK ../posix.cc ../posix.h)
 add_fmt_test(printf-test test-main)
 foreach (target format-test printf-test)
   if (CMAKE_COMPILER_IS_GNUCXX)
diff --git a/test/format-test.cc b/test/format-test.cc
index d69fce55..8e87911b 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -35,6 +35,13 @@
 #include <memory>
 #include <sstream>
 
+// Include format.cc instead of format.h to test implementation-specific stuff.
+#include "format.cc"
+#include "util.h"
+#include "gtest-extra.h"
+
+#include <stdint.h>
+
 #if defined(_WIN32) && !defined(__MINGW32__)
 // Fix MSVC warning about "unsafe" fopen.
 FILE *safe_fopen(const char *filename, const char *mode) {
@@ -45,12 +52,6 @@ FILE *safe_fopen(const char *filename, const char *mode) {
 #define fopen safe_fopen
 #endif
 
-#include "format.h"
-#include "util.h"
-#include "gtest-extra.h"
-
-#include <stdint.h>
-
 #undef min
 #undef max
 
@@ -1230,7 +1231,7 @@ TEST(FormatterTest, FormatNaN) {
   double nan = std::numeric_limits<double>::quiet_NaN();
   EXPECT_EQ("nan", format("{}", nan));
   EXPECT_EQ("+nan", format("{:+}", nan));
-  if (fmt::internal::signbit_noinline(-nan))
+  if (getsign(-nan))
     EXPECT_EQ("-nan", format("{}", -nan));
   else
     fmt::print("Warning: compiler doesn't handle negative NaN correctly");