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CHANGELOG.md

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Changelog

v0.7 - 10/11/2024

Changed

  • Disable -Wunused-function with -std=c89/90, since it would cause bogus warnings with math.h, because libc vendors use __inline in standard headers.
  • Parse qualifiers and storage class after tag definition. e.g. 
        struct s0 { int x; } static;           // OK, but deprecated since C23
    struct s1 { int y; } const;            // 'const' is ignored, emit warning
    struct s2 { int z; } const typedef s2; // Error
    Other compilers accept the third one, but they seem to be confused about it as well.
  • Collapse -Wattributes and -Wignore-attributes into one option.
  • Enable -Wtautological-overlap-compare with -Wall.
  • More precise diagnostic message for mismatching argument count with variadic functions.
  • Use SSE4.1 instructions for _mm_set* when -msse4.1 is set.
  • Disable -gcolumn-info by default, since gdb ignores it anyway.
  • Enable SSE version of neg IR instruction by default.
  • Mitigate UB on x64 for __builtin_ctz(0), by encoding bsf with the rep prefix.
  • Remove functions called only by unused functions (enabled by default).

Added

  • Add universal charater names for strings and characters.

  • Add partial C23 support with the -std=c23 switch:

    • Add keywords alignas, alingof, static_assert, thread_local, typeof_unqual, constexpr.
    • Add __has_c_attribute.
    • Parse the new attribute syntax [[]].
    • Predefine standard macros: __STDC_UTF_16__, __STDC_UTF_32__.
    • Add digit separators.
    • Add predefined constants: true, false and nullptr.
    • foo() becomes equivalent to foo(void).
    • Add type inference with auto. Missing bit-fields initializers and traditional mode e.g. auto int x will be (incorrectly) treated as an error.
    • Parse declarations after labels.
    • Add standard attributes: unsequenced, reproducible, nodiscard, deprecated, maybe_unused, noreturn, fallthrough.
    • Add enum type specifier.

  • Add -Wextern-initializer, enabled by default.

  • Add -Wimplicit-fallthrough.

  • Warn about assignments to read-only locations. e.g. "foo"[x] = 'a';.

  • Add attribute nodebug.

  • Add inline codegen for __builtin_memset also for non zero initialization values.

  • Add debug-info for bitfields.

  • Add __builtin_memcmp with inline simd codegen, when the size is known at compile time.

  • Add argument checking for intrinsics requiring a constant integer argument within a certain range.

  • Start riscv64 backend.

    • Add -march=rv64g option.
    • Predefine macros: __riscv, ... to complete

  • arm64 backend

    • Add codegen for __builtin_bswap/ctz/clz/clrsb/parity/ffs/popcnt.
    • Handle non-zero clear byte for __builtin_memset.
    • Encode bitmask (logical) immediates.

  • x64 backned:

    • Add all AVX/AVX2 intrinsics, except for: _mm_broadcastb_epi*, _mm256_broadcastb_epi* which use EVEX encoding.
    • Add BMI1, MOVBE, _rdtscp, RDRAND, RDSEED, RDPID intrinsics.
    • Predefine __BMI__, __BMI2__, __MOVBE__, __RDSEED__, __RDPID__, __RDRND__, __AVX__, __AVX2__.
    • Add -mbmi, -mbmi2, -mrdrnd, -mrdseed, -mrdpid, -mmovbe, -mavx, -mavx2 command-line options.

  • Build more stuff: 8080, BearSSL, libcox, luigi, mg, oed, parson, pl0c, qbe, utf8.h, vce, z80.

Removed

  • Remove -Wcast-function-type.

Fixed

  • Fix segfault caused by recursive enum valuation in compile-time __builtin_overflow_*, caused by typeof. Now it's possible to write: 
    #define __builtin_add_overflow_p(a,b) __builtin_add_overflow(a, b, (typeof((a) + (b))*)0)
enum {
    A = 0x7FFFFFFF,
    B = 3,
    C = __builtin_add_overflow_p(A, B) ? 0 : A + B,
};
  • Fix incorrect sizeof parsing with un-parenthesized member expressions, like: sizeof ((struct foo *)0)->bar.
  • Fix multi-byte escape sequences for UTF16/32 strings/characters.
  • Fix undiagnosed -Wdangling-else.
  • Fix bug with -Wtautological-overlap-compare.
  • Fix debug-info issues
    • Inspect static local variables.
    • Step on multi-line conditional expressions.
    • Inspect anonymous enums.
  • Fix bitfield related bugs.
  • Fix a bug with -Wpointer-to-int-cast.

v0.6 - 28/07/2024

Changed

  • Do not emit unused static functions by default. This reduces compile-time and if the user want to run a function in the debugger it can always mark it with the used attribute.
  • Always reduce unsigned divides by a power of two.
  • Rename -march=host into -march=native for compatiblity with GCC.
  • Enable -Wreturn-type by default.
  • Temporarily disable -Wsequence-point, since it's giving false positive on real software.
  • Incorporate -Woverlength-strings into -Wpedantic.
  • Merge -m and -march into a single option.
  • Emit movdqa instead of movaps for memory ops, when the vector subtype is an integer type.
  • Improve diagnostic for argument count mismatch errors. Use the first argument position having incompatible type when there is one, otherwise use the function call '(' position like before.
  • Accept storage class after tag type specifiers in declarations/definitions.
  • Disable -Wmisleading-indentation, since it sometimes gives false positives.

Added

  • Add attributes: noinline, always_inline, hot, cold and noipa.
  • Parse attributes after pointer types. e.g. void *__attribute__((noinline)) foo();
  • Add warnings: -Wstack-usage, -Wcompare-distinct-pointer-types, -Winline, -Wunused-macros=main, -Wunused-macros=nosys, -Wunused-macros=all, -Wenum-int-mismatch, -Wtautological-overlap-compare, -Winvalid-memory-model, -Wundefined-internal.
  • Add options: -pthread, -foptim-report, -finline, -msse3, -mssse3, -msse4, -msse4.1, -msse4.2.
  • Add builtins: __atomic_*, __builtin_frame_address, __builtin_return_address, __builtin_stack_address.
  • Implement __builtin_unreachable for -O1 and -O0.
  • Add optimization passes:
    • Register promotion.
    • Dead code elimination.
    • Constant propagation.
    • Common sub-expression elimination.
    • Strength reduction.
    • Inlining.
    • Dead argument elimination.
    • Various form of CFG reductions.
  • Omit frame prolog/epilog for leaf functions with -O1, when possible.
  • Restore SWITCH reduction to range change.
  • Add SEL reduction for power of 2. e.g. if (cond) flags |= The_Flag => flags |= (cond << bit(The_Flag))
  • Build more open-source projects: chibicc, cproc, gc, gennan, quadsort, renderer, rpng, siod, sqlite3, tinn.

Removed

  • Remove -save-temps.
  • Remove -Wformat-security.
  • Remove old debug-info code for recording type qualifiers. Pros:
    • they are not needed to actually debug an application,
    • they make the executable bigger,
    • implementation-wise they are akward,
    • most people probably don't care. Cons:
    • One might want to inspect debug-info for getting AST info, but again we provide better options for that.
  • Remove file_scope attribute. Now it's a custom attribute.

Fixed

  • Fix warnings: -Wignored-qualifiers, -Wmissing-prototypes, -Wreturn-local-addr, -Wshift-negative-value, -Wtype-limits, -Wenum-conversion, -Wtautological-compare.
  • Fix linking bug caused by missing some CRT objects.
  • Fix self-hosting regressions.
  • Fix edge case bugs in initializers.

v0.5 - 01/04/2024

Changed

  • Show function definition on calls with mismatch argument count.
  • -Wpedantic with -std=c89 is best effort, it won't catch all later features uses. Most people have move on to later standards, so it doesn't make sense to add complexity for this.
  • Display helper message for invalid multi-dimensional arrays only once, since it's always the same.
  • Change __FUNCTION__ behavior like MSVC.
  • Compile as C11 by default.
  • Change fatal exit code from 130 to 1.
  • Make operator overloading ignore typedefs.

Added

  • Add spellchecking for undeclared members.
  • Add -Wunused-but-set-variable.
  • Add basic support for inline assembly, just templates, outputs and clobbers.
  • Add basic cross-compilation support for arm64.
  • Add -Wunused-result and warn_unused_result attribute.
  • Add -Wunused-parameter.
  • Add warning for extern variables with initializer.
  • Add UTF8/16 string and character literals.
  • Add #pragma pack.
  • Add #pragma message.
  • Add #pragma warning.
  • Add #pragma error.
  • Add #pragma dependency.
  • Add #elifdef/elifndef.
  • Add -Wunused-macros.
  • Show macro expansion in error messages.
  • Generate code for run-time __builtin_offsetof.
  • Spellcheck undeclared identifiers.
  • Spellcheck invalid cpp directives.

Removed

  • Do not support VLA, always treat them as errors.
  • Remove -Wmultichar. Treat it as an error, since it is implementation defined.
  • Remove cast to union extension.
  • Remove -fsigned-char.
  • Remove -fauto-typedef. Implement it as a plugin.

Fixed

  • Restore -Wbad-function-cast.
  • Properly treat _Generic expression as lvalue when the selected expression is indeed an lvalue.
  • Fix bugs related to lvalue-to-rvalue conversion.

v0.4 - 30/12/2023

Changed

  • Rename -fzii into -ftrivial-auto-var-init to be compatible with GCC and add support for pattern initialization.

  • Fuse load followed by arithmetic instruction. Enable this by default, since the compiler's performance didn't resent much.

  • Do not allow extern void variables. For some reason GCC and CLANG allow them, while MSVC doesn't.

  • Set max array size to 4GB. MSVC limit is 2GB, CLANG limit is much bigger (thousand of TB) and GCC even larger (__SIZE_MAX__/2 or something). In practice the max stack size is around 10-30MB and allocating arrays that big is unusual. Maybe we should add a flag (-fstack-limit maybe?) to allow huge arrays, since they might be used for debugging purposes.

  • Disable __label__ parsing.

  • Do not allow unicode identifiers, since it adds complexity for an arguably useless feature (i.e. code is written in english).

    It's also a source of security vulnerabilities.

Added

  • Add -Wreturn-type
  • Add -Wconversion
  • Emit debug info for SIMD types.
  • Add __builtin_unreachable
  • Predefine conditional feature macros:
    • __STDC_NO_ATOMICS__,
    • __STDC_NO_COMPLEX__,
    • __STDC_NO_THREADS__,
    • __STDC_NO_VLA__.
  • Add consecutive immediate stores fusion optimization.
  • Add -x option to select the language for input files.
  • Add -fswitch-strategy and __builtin_switch_strategy for selecting the switch lowering method.
  • Add __builtin_memset_strategy and __builtin_memcpy_strategy.
  • Plugin API for extending the compiler:
    • AST inspection,
    • Custom attributes and builtins,
    • Callbacks
  • Add optimize attribute.
  • Support consencutive label definitions in the assembler.
  • Cleanup operator overloading attribute: more operands, symmetric property, better error checking.
  • Encode clflush, clflushopt, cldemote, clrssbsy, bt, btc, btr and bts.
  • Add signed integer overflow run-time checking with -fcheck-signed-overflow.
  • Improve code generation for _mm_set_* intrinsics with homogeneous arguments, using SSE3/SSSE3 intrinsics when available.
  • __builtin_memset/memcpy are now considered intrinsics.
  • Add __builtin_trap.
  • Add overflow builtins. Do not add the _p variants since they are redundant.
  • Add uninitialized attribute for -fzii.
  • Add -Wvarargs.
  • Allow the user to specify built-in functions through -fplugin.
  • Read string literals and character constants in utf8 and convert them in the requested encoding. Wide string literals and character constants are encoded in utf32.

Removed

  • Remove the additional helper message for unterminated condition, since it cause more confusion.
  • Remove RTTI. The major drawback is additional work in the compiler, plus you can't debug the generated code. In contrast the same feature could be implemented through a meta-programming preprocessing pass using the pluing API.
  • Remove -Wlong-long, since it's also enabled by -Wpedantic and nobody care about long long anyway.

Fixed

  • Fix -Wsign-compare
  • Fix -Waddress
  • Restore -Wnonnull, -Wnonnull-compare, -Wunused-function, -Wunused-label, -Wunused-variable, -Wsizeof-pointer-memaccess.
  • Restore __builtin_nan
  • Restore __builtin_cpu_supports.
  • Restore -Woverflow, -Wbool-operation, -Wchar-subscripts, -Wint-in-bool-context, -Wcomment, -Wdouble-promotion, -Wtautological-compare, -Wsizeof-array-argument.
  • Restore type inference with __auto_type or with auto in C23.

v0.3 - 01/10/2023

Added

  • Internal assembler for x86_64
  • Bit-fields.
  • Thread-local storage.

Fixed

  • Fix x87 register allocation.