math: Avoid signed integer overflow when intrinsics are available

The `math(EXPR)` command documents that results must fit in a 64-bit
signed integer.  When built with compilers that offer the relevant
intrinsics, detect overflow and issue warnings.

.gitlab/ci/configure_debian13_aarch64_ninja.cmake

@@ -106,6 +106,7 @@ set(CMake_TEST_IPO_WORKS_C "ON" CACHE BOOL "")
 set(CMake_TEST_IPO_WORKS_CXX "ON" CACHE BOOL "")
 set(CMake_TEST_IPO_WORKS_Fortran "ON" CACHE BOOL "")
 set(CMake_TEST_JQ "/usr/bin/jq" CACHE PATH "")
+set(CMake_TEST_MATH_OVERFLOW ON CACHE BOOL "")
 set(CMake_TEST_Qt5 "ON" CACHE BOOL "")
 set(CMake_TEST_TLS_VERIFY_URL "https://gitlab.kitware.com" CACHE STRING "")
 set(CMake_TEST_TLS_VERIFY_URL_BAD "https://badtls-expired.kitware.com" CACHE STRING "")

.gitlab/ci/configure_debian13_ninja_common.cmake

@@ -106,6 +106,7 @@ set(CMake_TEST_IPO_WORKS_C "ON" CACHE BOOL "")
 set(CMake_TEST_IPO_WORKS_CXX "ON" CACHE BOOL "")
 set(CMake_TEST_IPO_WORKS_Fortran "ON" CACHE BOOL "")
 set(CMake_TEST_JQ "/usr/bin/jq" CACHE PATH "")
+set(CMake_TEST_MATH_OVERFLOW ON CACHE BOOL "")
 set(CMake_TEST_Qt5 "ON" CACHE BOOL "")
 set(CMake_TEST_TLS_VERIFY_URL "https://gitlab.kitware.com" CACHE STRING "")
 set(CMake_TEST_TLS_VERIFY_URL_BAD "https://badtls-expired.kitware.com" CACHE STRING "")

.gitlab/ci/configure_fedora43_bullseye_coverage.cmake

@@ -12,6 +12,7 @@ set(CMAKE_SKIP_BOOTSTRAP_TEST TRUE CACHE BOOL "")
 set(ENV{KWSYS_TEST_PROCESS_1_COUNT} 11)
 
 set(CMake_TEST_GUI "ON" CACHE BOOL "")
+set(CMake_TEST_MATH_OVERFLOW ON CACHE BOOL "")
 set(CMake_TEST_MODULE_COMPILATION "named,compile_commands,collation,partitions,internal_partitions,export_bmi,install_bmi,shared,bmionly,build_database,import_std23" CACHE STRING "")
 set(CMake_TEST_TLS_VERIFY_URL "https://gitlab.kitware.com" CACHE STRING "")
 set(CMake_TEST_TLS_VERIFY_URL_BAD "https://badtls-expired.kitware.com" CACHE STRING "")

.gitlab/ci/configure_fedora43_gcc_gcov.cmake

@@ -1,4 +1,5 @@
 set(CMake_TEST_GUI "ON" CACHE BOOL "")
+set(CMake_TEST_MATH_OVERFLOW ON CACHE BOOL "")
 set(CMake_TEST_MODULE_COMPILATION "named,compile_commands,collation,partitions,internal_partitions,export_bmi,install_bmi,shared,bmionly,build_database,import_std23" CACHE STRING "")
 set(CMake_TEST_TLS_VERIFY_URL "https://gitlab.kitware.com" CACHE STRING "")
 set(CMake_TEST_TLS_VERIFY_URL_BAD "https://badtls-expired.kitware.com" CACHE STRING "")

.gitlab/ci/configure_fedora43_makefiles.cmake

@@ -109,6 +109,7 @@ if (NOT "$ENV{CMAKE_CI_NIGHTLY}" STREQUAL "")
   set(CMake_TEST_ISPC "ON" CACHE STRING "")
 endif()
 set(CMake_TEST_LOCALE_CHARSET "ISO-8859-1" CACHE STRING "")
+set(CMake_TEST_MATH_OVERFLOW ON CACHE BOOL "")
 set(CMake_TEST_Qt5 "ON" CACHE BOOL "")
 set(CMake_TEST_TLS_VERIFY_URL "https://gitlab.kitware.com" CACHE STRING "")
 set(CMake_TEST_TLS_VERIFY_URL_BAD "https://badtls-expired.kitware.com" CACHE STRING "")

.gitlab/ci/configure_fedora43_ninja.cmake

@@ -5,6 +5,7 @@ if (NOT "$ENV{CMAKE_CI_NIGHTLY}" STREQUAL "")
   set(CMake_TEST_ISPC "ON" CACHE STRING "")
 endif()
 set(CMake_TEST_LOCALE_CHARSET "UTF-8" CACHE STRING "")
+set(CMake_TEST_MATH_OVERFLOW ON CACHE BOOL "")
 set(CMake_TEST_MODULE_COMPILATION "named,compile_commands,collation,partitions,internal_partitions,export_bmi,install_bmi,shared,bmionly,build_database,import_std23" CACHE STRING "")
 set(CMake_TEST_Rust "ON" CACHE STRING "")
 set(CMake_TEST_TLS_VERIFY_URL "https://gitlab.kitware.com" CACHE STRING "")

.gitlab/ci/configure_macos_arm64_ninja.cmake

@@ -7,6 +7,7 @@ set(CMake_TEST_FindOpenMP_C "ON" CACHE BOOL "")
 set(CMake_TEST_FindOpenMP_CXX "ON" CACHE BOOL "")
 set(CMake_TEST_GUI "ON" CACHE BOOL "")
 set(CMake_TEST_LOCALE_CHARSET "UTF-8" CACHE STRING "")
+set(CMake_TEST_MATH_OVERFLOW ON CACHE BOOL "")
 set(CMake_TEST_TLS_VERIFY_URL "https://gitlab.kitware.com" CACHE STRING "")
 set(CMake_TEST_TLS_VERIFY_URL_BAD "https://badtls-expired.kitware.com" CACHE STRING "")
 set(CMake_TEST_TLS_VERSION "1.2" CACHE STRING "")

.gitlab/ci/configure_macos_x86_64_makefiles.cmake

@@ -6,6 +6,7 @@ set(CMake_TEST_GUI "ON" CACHE BOOL "")
 if (NOT "$ENV{CMAKE_CI_NIGHTLY}" STREQUAL "")
   set(CMake_TEST_ISPC "ON" CACHE STRING "")
 endif()
+set(CMake_TEST_MATH_OVERFLOW ON CACHE BOOL "")
 set(CMake_TEST_TLS_VERIFY_URL "https://gitlab.kitware.com" CACHE STRING "")
 set(CMake_TEST_TLS_VERIFY_URL_BAD "https://badtls-expired.kitware.com" CACHE STRING "")
 set(CMake_TEST_TLS_VERSION "1.2" CACHE STRING "")

.gitlab/ci/configure_macos_x86_64_ninja.cmake

@@ -10,6 +10,7 @@ if (NOT "$ENV{CMAKE_CI_NIGHTLY}" STREQUAL "")
   set(CMake_TEST_ISPC "ON" CACHE STRING "")
 endif()
 set(CMake_TEST_LOCALE_CHARSET "UTF-8" CACHE STRING "")
+set(CMake_TEST_MATH_OVERFLOW ON CACHE BOOL "")
 set(CMake_TEST_TLS_VERIFY_URL "https://gitlab.kitware.com" CACHE STRING "")
 set(CMake_TEST_TLS_VERIFY_URL_BAD "https://badtls-expired.kitware.com" CACHE STRING "")
 set(CMake_TEST_TLS_VERSION "1.2" CACHE STRING "")

Source/cmExprParserHelper.cxx

@@ -100,6 +100,11 @@ void cmExprParserHelper::Error(char const* str)
   this->ErrorString = ostr.str();
 }
 
+void cmExprParserHelper::Warning(std::string str)
+{
+  this->WarningString = cmStrCat(this->WarningString, std::move(str), '\n');
+}
+
 void cmExprParserHelper::UnexpectedChar(char c)
 {
   unsigned long pos = static_cast<unsigned long>(this->InputBufferPos);
@@ -121,27 +126,63 @@ void cmExprParserHelper::SetError(std::string errorString)
 
 std::int64_t cmExprParserHelper::ShL(std::int64_t l, std::int64_t r)
 {
-  return l << r;
+  if (l < 0) {
+    this->Warning(
+      cmStrCat("left shift of negative value in:\n  ", l, " << ", r));
+  }
+  if (r < 0) {
+    this->Warning(
+      cmStrCat("shift exponent is negative in:\n  ", l, " << ", r));
+    r &= 0x3F;
+  }
+  if (r >= 64) {
+    this->Warning(
+      cmStrCat("shift exponent is too large in:\n  ", l, " << ", r));
+    r &= 0x3F;
+  }
+  return static_cast<std::int64_t>(static_cast<std::uint64_t>(l) << r);
 }
 
 std::int64_t cmExprParserHelper::ShR(std::int64_t l, std::int64_t r)
 {
+  if (r < 0) {
+    this->Warning(
+      cmStrCat("shift exponent is negative in:\n  ", l, " >> ", r));
+    r &= 0x3F;
+  }
+  if (r >= 64) {
+    this->Warning(
+      cmStrCat("shift exponent is too large in:\n  ", l, " >> ", r));
+    r &= 0x3F;
+  }
   return l >> r;
 }
 
 std::int64_t cmExprParserHelper::Add(std::int64_t l, std::int64_t r)
 {
-  return l + r;
+  std::int64_t sum;
+  if (this->AddOverflow(l, r, &sum)) {
+    this->Warning(cmStrCat("signed integer overflow in:\n  ", l, " + ", r));
+  }
+  return sum;
 }
 
 std::int64_t cmExprParserHelper::Sub(std::int64_t l, std::int64_t r)
 {
-  return l - r;
+  std::int64_t diff;
+  if (this->SubOverflow(l, r, &diff)) {
+    this->Warning(cmStrCat("signed integer overflow in:\n  ", l, " - ", r));
+  }
+  return diff;
 }
 
 std::int64_t cmExprParserHelper::Mul(std::int64_t l, std::int64_t r)
 {
-  return l * r;
+  std::int64_t prod;
+  if (this->MulOverflow(l, r, &prod)) {
+    this->Warning(cmStrCat("signed integer overflow in:\n  ", l, " * ", r));
+  }
+  return prod;
 }
 
 std::int64_t cmExprParserHelper::Div(std::int64_t l, std::int64_t r)
@@ -159,3 +200,73 @@ std::int64_t cmExprParserHelper::Mod(std::int64_t l, std::int64_t r)
   }
   return l % r;
 }
+
+// The __has_builtin preprocessor check was added in Clang 2.6 and GCC 10.
+// The __builtin_X_overflow intrinsics were added in Clang 3.4 and GCC 5.
+#ifndef __has_builtin
+#  if defined(__GNUC__) && __GNUC__ >= 5
+#    define __has_builtin(x) 1
+#  else
+#    define __has_builtin(x) 0
+#  endif
+#endif
+
+bool cmExprParserHelper::AddOverflow(long l, long r, long* p)
+{
+#if __has_builtin(__builtin_saddl_overflow)
+  return __builtin_saddl_overflow(l, r, p);
+#else
+  *p = l + r;
+  return false;
+#endif
+}
+
+bool cmExprParserHelper::AddOverflow(long long l, long long r, long long* p)
+{
+#if __has_builtin(__builtin_saddll_overflow)
+  return __builtin_saddll_overflow(l, r, p);
+#else
+  *p = l + r;
+  return false;
+#endif
+}
+
+bool cmExprParserHelper::SubOverflow(long l, long r, long* p)
+{
+#if __has_builtin(__builtin_ssubl_overflow)
+  return __builtin_ssubl_overflow(l, r, p);
+#else
+  *p = l - r;
+  return false;
+#endif
+}
+
+bool cmExprParserHelper::SubOverflow(long long l, long long r, long long* p)
+{
+#if __has_builtin(__builtin_ssubll_overflow)
+  return __builtin_ssubll_overflow(l, r, p);
+#else
+  *p = l - r;
+  return false;
+#endif
+}
+
+bool cmExprParserHelper::MulOverflow(long l, long r, long* p)
+{
+#if __has_builtin(__builtin_smull_overflow)
+  return __builtin_smull_overflow(l, r, p);
+#else
+  *p = l * r;
+  return false;
+#endif
+}
+
+bool cmExprParserHelper::MulOverflow(long long l, long long r, long long* p)
+{
+#if __has_builtin(__builtin_smulll_overflow)
+  return __builtin_smulll_overflow(l, r, p);
+#else
+  *p = l * r;
+  return false;
+#endif
+}

Source/cmExprParserHelper.h

@@ -23,6 +23,7 @@ public:
 
   int LexInput(char* buf, int maxlen);
   void Error(char const* str);
+  void Warning(std::string str);
 
   void SetResult(std::int64_t value);
 
@@ -42,6 +43,13 @@ public:
   std::int64_t Div(std::int64_t l, std::int64_t r);
   std::int64_t Mod(std::int64_t l, std::int64_t r);
 
+  static bool AddOverflow(long l, long r, long* p);
+  static bool AddOverflow(long long l, long long r, long long* p);
+  static bool SubOverflow(long l, long r, long* p);
+  static bool SubOverflow(long long l, long long r, long long* p);
+  static bool MulOverflow(long l, long r, long* p);
+  static bool MulOverflow(long long l, long long r, long long* p);
+
 private:
   std::string::size_type InputBufferPos;
   std::string InputBuffer;

Tests/RunCMake/CMakeLists.txt

@@ -769,6 +769,9 @@ add_RunCMake_test(include_directories)
 add_RunCMake_test(include_guard)
 add_RunCMake_test(list)
 add_RunCMake_test(load_cache)
+if(DEFINED CMake_TEST_MATH_OVERFLOW)
+  list(APPEND math_ARGS -DCMake_TEST_MATH_OVERFLOW=${CMake_TEST_MATH_OVERFLOW})
+endif()
 add_RunCMake_test(math)
 add_RunCMake_test(message)
 add_RunCMake_test(option)

Tests/RunCMake/math/Overflow-stderr.txt

@@ -0,0 +1,63 @@
+^CMake Warning \(dev\) at [^
+]+/Tests/RunCMake/math/Overflow\.cmake:[0-9]+ \(math\):
+  left shift of negative value in:
+
+    -4 << 1
+
+This warning is for project developers\.  Use -Wno-dev to suppress it\.
++
+CMake Warning \(dev\) at [^
+]+/Tests/RunCMake/math/Overflow\.cmake:[0-9]+ \(math\):
+  shift exponent is negative in:
+
+    4 << -63
+
+This warning is for project developers\.  Use -Wno-dev to suppress it\.
++
+CMake Warning \(dev\) at [^
+]+/Tests/RunCMake/math/Overflow\.cmake:[0-9]+ \(math\):
+  shift exponent is negative in:
+
+    4 >> -63
+
+This warning is for project developers\.  Use -Wno-dev to suppress it\.
++
+CMake Warning \(dev\) at [^
+]+/Tests/RunCMake/math/Overflow\.cmake:[0-9]+ \(math\):
+  shift exponent is too large in:
+
+    4 << 65
+
+This warning is for project developers\.  Use -Wno-dev to suppress it\.
++
+CMake Warning \(dev\) at [^
+]+/Tests/RunCMake/math/Overflow\.cmake:[0-9]+ \(math\):
+  shift exponent is too large in:
+
+    4 >> 65
+
+This warning is for project developers\.  Use -Wno-dev to suppress it\.
++
+CMake Warning \(dev\) at [^
+]+/Tests/RunCMake/math/Overflow\.cmake:[0-9]+ \(math\):
+  signed integer overflow in:
+
+    9223372036854775807 \+ 1
+
+This warning is for project developers\.  Use -Wno-dev to suppress it\.
++
+CMake Warning \(dev\) at [^
+]+/Tests/RunCMake/math/Overflow\.cmake:[0-9]+ \(math\):
+  signed integer overflow in:
+
+    -9223372036854775807 - 2
+
+This warning is for project developers\.  Use -Wno-dev to suppress it\.
++
+CMake Warning \(dev\) at [^
+]+/Tests/RunCMake/math/Overflow\.cmake:[0-9]+ \(math\):
+  signed integer overflow in:
+
+    9223372036854775807 \* 2
+
+This warning is for project developers\.  Use -Wno-dev to suppress it\.$

Tests/RunCMake/math/Overflow-stdout.txt

@@ -0,0 +1,9 @@
+^-- -4 <<   1: -8
+-- -4 >>   1: -2
+--  4 << -63: 8
+--  4 >> -63: 2
+--  4 <<  65: 8
+--  4 >>  65: 2
+--  0x7FFFFFFFFFFFFFFF \+ 1: -9223372036854775808
+-- -0x7FFFFFFFFFFFFFFF - 2: 9223372036854775807
+--  0x7FFFFFFFFFFFFFFF \* 2: -2$

Tests/RunCMake/math/Overflow.cmake

@@ -0,0 +1,14 @@
+foreach(expr IN ITEMS
+    "-4 <<   1"
+    "-4 >>   1"
+    " 4 << -63"
+    " 4 >> -63"
+    " 4 <<  65"
+    " 4 >>  65"
+    " 0x7FFFFFFFFFFFFFFF + 1"
+    "-0x7FFFFFFFFFFFFFFF - 2"
+    " 0x7FFFFFFFFFFFFFFF * 2"
+  )
+  math(EXPR result "${expr}")
+  message(STATUS "${expr}: ${result}")
+endforeach()

Tests/RunCMake/math/RunCMakeTest.cmake

@@ -8,3 +8,7 @@ run_cmake(MATH-InvalidExpression)
 run_cmake(MATH-ToleratedExpression)
 run_cmake(MATH-DivideByZero)
 run_cmake(MATH-ModByZero)
+
+if(CMake_TEST_MATH_OVERFLOW)
+  run_cmake_script(Overflow)
+endif()