CI: work-around zig cc mips bad codegen for hard-float

.github/workflows/ci.yml

@@ -466,8 +466,9 @@ jobs:
           - { zig_target: i386-linux-musl, qemu: qemu-i386 }
           # { zig_target: i386-linux-musl, qemu: qemu-i386, zig_pic: -fPIE }
           - { zig_target: i386-windows-gnu }
-          - { zig_target: mips-linux-musl }   # TODO: qemu
+          # mips and mipsel: bad hard-float code generation; see https://github.com/upx/upx/issues/788
-          - { zig_target: mipsel-linux-musl } # TODO: qemu
+          - { zig_target: mips-linux-musl, zig_flags: -msoft-float, qemu: qemu-mips }
+          - { zig_target: mipsel-linux-musl, zig_flags: -msoft-float, qemu: qemu-mipsel }
           - { zig_target: powerpc-linux-musl, qemu: qemu-ppc }
           - { zig_target: powerpc64-linux-musl, qemu: qemu-ppc64 }
           - { zig_target: powerpc64le-linux-musl, qemu: qemu-ppc64le }

CMakeLists.txt

@@ -254,9 +254,15 @@ endif()
 if(Threads_FOUND)
     foreach(f std_lock_guard.cpp)
         set(CMAKE_TRY_COMPILE_TARGET_TYPE "EXECUTABLE")
-        try_compile(result "${CMAKE_CURRENT_BINARY_DIR}"
+        if(NOT UPX_CONFIG_DISABLE_CXX_STANDARD)
-                    "${CMAKE_CURRENT_SOURCE_DIR}/misc/cmake/try_compile/${f}"
+            try_compile(result "${CMAKE_CURRENT_BINARY_DIR}"
-                    CXX_STANDARD 17 OUTPUT_VARIABLE output)
+                        "${CMAKE_CURRENT_SOURCE_DIR}/misc/cmake/try_compile/${f}"
+                        OUTPUT_VARIABLE output CXX_STANDARD 17)
+        else()
+            try_compile(result "${CMAKE_CURRENT_BINARY_DIR}"
+                        "${CMAKE_CURRENT_SOURCE_DIR}/misc/cmake/try_compile/${f}"
+                        OUTPUT_VARIABLE output)
+        endif()
         if(NOT result)
             # failed; under MinGW be sure to use the posix-threads and NOT the win32-threads version
             #message(STATUS "Threads FAILED: ${output}") # debug output from try_compile

misc/cmake/functions.cmake

@@ -197,6 +197,7 @@ function(upx_add_definitions) # ARGV; needs include(CheckCCompilerFlag)
     endif()
 endfunction()
 
+# useful for CI jobs: allow target extra compile options
 function(upx_add_target_extra_compile_options) # ARGV
     set(t "${ARGV0}")
     list(REMOVE_AT ARGV 0)

src/check/dt_check.cpp

@@ -323,6 +323,10 @@ struct TestIntegerWrap {
     static inline bool neg_eq(const T x) noexcept { return T(0) - x == x; }
 };
 
+//
+// basic exception handling
+//
+
 static noinline void throwSomeValue(int x) may_throw {
     if (x < 0)
         throw int(x);
@@ -342,6 +346,23 @@ static noinline void check_basic_cxx_exception_handling(void (*func)(int)) noexc
     assert_noexcept(cxx_exception_handling_works);
 }
 
+//
+// basic floating point to early catch bad codegen
+// (this has happened in the past with some exotic LLVM targets)
+//
+
+static noinline double sadd_a_b_div(upx_int64_t a, upx_int64_t b) { return (a + b) / 1000000.0; }
+static noinline double uadd_a_b_div(upx_uint64_t a, upx_uint64_t b) { return (a + b) / 1000000.0; }
+static noinline double ssub_a_b_div(upx_int64_t a, upx_int64_t b) { return (a - b) / 1000000.0; }
+static noinline double usub_a_b_div(upx_uint64_t a, upx_uint64_t b) { return (a - b) / 1000000.0; }
+
+static noinline void check_basic_floating_point(void) noexcept {
+    assert_noexcept(sadd_a_b_div(1000000, 1000000) == 2.0);
+    assert_noexcept(uadd_a_b_div(1000000, 1000000) == 2.0);
+    assert_noexcept(ssub_a_b_div(3000000, 1000000) == 2.0);
+    assert_noexcept(usub_a_b_div(3000000, 1000000) == 2.0);
+}
+
 } // namespace
 
 #define ACC_WANT_ACC_CHK_CH 1
@@ -360,6 +381,8 @@ void upx_compiler_sanity_check(void) noexcept {
         check_basic_cxx_exception_handling(throwSomeValue);
     }
 
+    check_basic_floating_point();
+
 #define ACC_WANT_ACC_CHK_CH 1
 #undef ACCCHK_ASSERT
 #define ACCCHK_ASSERT(expr) ACC_COMPILE_TIME_ASSERT(expr)