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Check unaligned array access.

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This commit is contained in:
Christoffer Lerno
2025-07-18 20:45:57 +02:00
parent f2babb6063
commit 2acf3c57c7
3 changed files with 82 additions and 0 deletions
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1
releasenotes.md
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@@ -23,6 +23,7 @@
- Suppress codegen of panic printing with when panic messages are set to "off".
- Implicit linking of libc math when libc math functions are used.
- Allow even smaller memory limits.
- Check unaligned array access.
### Fixes
- mkdir/rmdir would not work properly with substring paths on non-windows platforms.

17
src/compiler/llvm_codegen_expr.c
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@@ -764,6 +764,23 @@ static inline void llvm_emit_subscript(GenContext *c, BEValue *value, Expr *expr
return;
}
llvm_emit_subscript_addr(c, value, expr);
if (safe_mode_enabled() && value->alignment > 1 && !c->emitting_load_store_check && parent_type->type_kind != TYPE_ARRAY)
{
LLVMValueRef as_int = LLVMBuildPtrToInt(c->builder, value->value, llvm_get_type(c, type_usz), "");
LLVMValueRef align = llvm_const_int(c, type_usz, value->alignment);
LLVMValueRef rem = LLVMBuildURem(c->builder, as_int, align, "");
LLVMValueRef is_not_zero = LLVMBuildICmp(c->builder, LLVMIntNE, rem, llvm_get_zero(c, type_usz), "");
c->emitting_load_store_check = true;
BEValue value1;
BEValue value2;
llvm_value_set(&value1, align, type_usz);
llvm_value_set(&value2, rem, type_usz);
llvm_emit_panic_on_true(c, is_not_zero, "Unaligned pointer access detected", parent_expr->span, "Unaligned access: ptr %% %s = %s, use @unaligned_load / @unaligned_store for unaligned access.",
&value1, &value2);
c->emitting_load_store_check = false;
}
}
static inline void llvm_emit_pointer_offset(GenContext *c, BEValue *value, Expr *expr)

64
test/test_suite/expressions/unaligned_array_check.c3t Normal file
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@@ -0,0 +1,64 @@
// #target: macos-x64
// #safe: yes
module test;
import std;
fn int main()
{
char[35] x;
long[3] w;
long z = @unaligned_load(((long*)&x[1])[0], 1);
long y = ((long*)&x[1])[0];
long ww = w[1];
return 0;
}
/* #expect: test.ll
define i32 @main() #0 {
entry:
%x = alloca [35 x i8], align 16
%w = alloca [3 x i64], align 16
%z = alloca i64, align 8
%y = alloca i64, align 8
%taddr = alloca i64, align 8
%taddr2 = alloca i64, align 8
%varargslots = alloca [2 x %any], align 16
%indirectarg = alloca %"any[]", align 8
%ww = alloca i64, align 8
call void @llvm.memset.p0.i64(ptr align 16 %x, i8 0, i64 35, i1 false)
call void @llvm.memset.p0.i64(ptr align 16 %w, i8 0, i64 24, i1 false)
%ptradd = getelementptr inbounds i8, ptr %x, i64 1
%0 = load i64, ptr %ptradd, align 1
store i64 %0, ptr %z, align 8
%ptradd1 = getelementptr inbounds i8, ptr %x, i64 1
%1 = ptrtoint ptr %ptradd1 to i64
%2 = urem i64 %1, 8
%3 = icmp ne i64 %2, 0
%4 = call i1 @llvm.expect.i1(i1 %3, i1 false)
br i1 %4, label %panic, label %checkok
checkok: ; preds = %entry
%5 = load i64, ptr %ptradd1, align 8
store i64 %5, ptr %y, align 8
%ptradd4 = getelementptr inbounds i8, ptr %w, i64 8
%6 = load i64, ptr %ptradd4, align 8
store i64 %6, ptr %ww, align 8
ret i32 0
panic: ; preds = %entry
store i64 8, ptr %taddr, align 8
%7 = insertvalue %any undef, ptr %taddr, 0
%8 = insertvalue %any %7, i64 ptrtoint (ptr @"$ct.ulong" to i64), 1
store i64 %2, ptr %taddr2, align 8
%9 = insertvalue %any undef, ptr %taddr2, 0
%10 = insertvalue %any %9, i64 ptrtoint (ptr @"$ct.ulong" to i64), 1
store %any %8, ptr %varargslots, align 16
%ptradd3 = getelementptr inbounds i8, ptr %varargslots, i64 16
store %any %10, ptr %ptradd3, align 16
%11 = insertvalue %"any[]" undef, ptr %varargslots, 0
%"$$temp" = insertvalue %"any[]" %11, i64 2, 1
store %"any[]" %"$$temp", ptr %indirectarg, align 8
call void @std.core.builtin.panicf(ptr @.panic_msg, i64 94, ptr @.file, i64 24, ptr @.func, i64 4, i32 8, ptr byval(%"any[]") align 8 %indirectarg) #3
unreachable
}