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authorJo-Philipp Wich <jo@mein.io>2022-11-29 20:03:44 +0100
committerJo-Philipp Wich <jo@mein.io>2022-11-29 20:22:28 +0100
commiteac2add08377eb4ba8e43e7e6a8f385480ebd73b (patch)
tree0f9a074b8b4ebcb73b0487b4f2cce70ae9330857 /compiler.c
parent3497da1448f9b1d602e23c10977db0ce0188c959 (diff)
compiler: fix bytecode for logical assignments of properties
The compiler emitted incorrect bytecode for logical assignment operations on property expressions. The generated instructions left the stack in an unclean state when the assignment condition was not fulfilled, causing a stack layout mismatch between compiler and vm, leading to undefined variable accesses and other non-deterministic behavior. Solve this issue by rewriting the bytecode generation to yield an instruction sequence that does not leave garbage on the stack. The implementation is not optimal yet, as an expression in the form `obj.prop ||= val` will load `obj.prop` twice. This is acceptable for now as the load operation has no side effect, but should be solved in a better way by introducing new instructions that allow for swapping stack slots, allowing the vm to operate on a copy of the loaded value. Also rewrite the corresponding test case to trigger a runtime error on code versions before this fix. Fixes: fdc9b6a ("compiler: fix `??=`, `||=` and `&&=` logical assignment semantics") Signed-off-by: Jo-Philipp Wich <jo@mein.io>
Diffstat (limited to 'compiler.c')
-rw-r--r--compiler.c132
1 files changed, 68 insertions, 64 deletions
diff --git a/compiler.c b/compiler.c
index 6c336ae..6911477 100644
--- a/compiler.c
+++ b/compiler.c
@@ -575,6 +575,17 @@ uc_compiler_emit_jmp_dest(uc_compiler_t *compiler, size_t srcpos, uint32_t dest)
return chunk->count - 5;
}
+static size_t
+uc_compiler_emit_copy(uc_compiler_t *compiler, size_t srcpos, uint8_t depth)
+{
+ uc_chunk_t *chunk = uc_compiler_current_chunk(compiler);
+
+ uc_compiler_emit_insn(compiler, srcpos, I_COPY);
+ uc_compiler_emit_u8(compiler, 0, depth);
+
+ return chunk->count - 2;
+}
+
static ssize_t
uc_compiler_get_jmpaddr(uc_compiler_t *compiler, size_t off)
{
@@ -1153,93 +1164,104 @@ static void
uc_compiler_emit_variable_copy(uc_compiler_t *compiler, uc_value_t *var)
{
if (!var) {
- uc_compiler_emit_insn(compiler, 0, I_COPY);
- uc_compiler_emit_u8(compiler, 0, 1);
- uc_compiler_emit_insn(compiler, 0, I_COPY);
- uc_compiler_emit_u8(compiler, 0, 1);
+ uc_compiler_emit_copy(compiler, 0, 1);
+ uc_compiler_emit_copy(compiler, 0, 1);
}
uc_compiler_emit_variable_rw(compiler, var, 0);
}
static void
-uc_compiler_compile_and_common(uc_compiler_t *compiler, bool assignment, uc_value_t *var)
+uc_compiler_compile_and(uc_compiler_t *compiler)
{
uc_chunk_t *chunk = uc_compiler_current_chunk(compiler);
size_t jmpz_off;
- if (assignment)
- uc_compiler_emit_variable_copy(compiler, var);
-
- uc_compiler_emit_insn(compiler, 0, I_COPY);
- uc_compiler_emit_u8(compiler, 0, 0);
+ uc_compiler_emit_copy(compiler, 0, 0);
jmpz_off = uc_compiler_emit_jmpz(compiler, 0);
uc_compiler_emit_insn(compiler, 0, I_POP);
+ uc_compiler_parse_precedence(compiler, P_AND);
+ uc_compiler_set_jmpaddr(compiler, jmpz_off, chunk->count);
+}
- if (assignment) {
- uc_compiler_parse_precedence(compiler, P_ASSIGN);
- uc_compiler_emit_variable_rw(compiler, var, TK_ASSIGN);
- }
- else {
- uc_compiler_parse_precedence(compiler, P_AND);
- }
+static void
+uc_compiler_compile_and_assignment(uc_compiler_t *compiler, uc_value_t *var)
+{
+ uc_chunk_t *chunk = uc_compiler_current_chunk(compiler);
+ size_t jmpz_off;
+ uc_compiler_emit_variable_copy(compiler, var);
+ uc_compiler_emit_copy(compiler, 0, 0);
+ jmpz_off = uc_compiler_emit_jmpz(compiler, 0);
+ uc_compiler_emit_insn(compiler, 0, I_POP);
+ uc_compiler_parse_precedence(compiler, P_ASSIGN);
uc_compiler_set_jmpaddr(compiler, jmpz_off, chunk->count);
+ uc_compiler_emit_variable_rw(compiler, var, TK_ASSIGN);
}
static void
-uc_compiler_compile_or_common(uc_compiler_t *compiler, bool assignment, uc_value_t *var)
+uc_compiler_compile_or(uc_compiler_t *compiler)
{
uc_chunk_t *chunk = uc_compiler_current_chunk(compiler);
size_t jmpz_off, jmp_off;
- if (assignment)
- uc_compiler_emit_variable_copy(compiler, var);
-
- uc_compiler_emit_insn(compiler, 0, I_COPY);
- uc_compiler_emit_u8(compiler, 0, 0);
+ uc_compiler_emit_copy(compiler, 0, 0);
jmpz_off = uc_compiler_emit_jmpz(compiler, 0);
jmp_off = uc_compiler_emit_jmp(compiler, 0);
uc_compiler_set_jmpaddr(compiler, jmpz_off, chunk->count);
uc_compiler_emit_insn(compiler, 0, I_POP);
+ uc_compiler_parse_precedence(compiler, P_OR);
+ uc_compiler_set_jmpaddr(compiler, jmp_off, chunk->count);
+}
- if (assignment) {
- uc_compiler_parse_precedence(compiler, P_ASSIGN);
- uc_compiler_emit_variable_rw(compiler, var, TK_ASSIGN);
- }
- else {
- uc_compiler_parse_precedence(compiler, P_OR);
- }
+static void
+uc_compiler_compile_or_assignment(uc_compiler_t *compiler, uc_value_t *var)
+{
+ uc_chunk_t *chunk = uc_compiler_current_chunk(compiler);
+ size_t jmpz_off, jmp_off;
+ uc_compiler_emit_variable_copy(compiler, var);
+ jmpz_off = uc_compiler_emit_jmpz(compiler, 0);
+ uc_compiler_emit_variable_rw(compiler, var, 0);
+ jmp_off = uc_compiler_emit_jmp(compiler, 0);
+ uc_compiler_set_jmpaddr(compiler, jmpz_off, chunk->count);
+ uc_compiler_parse_precedence(compiler, P_ASSIGN);
+ uc_compiler_emit_variable_rw(compiler, var, TK_ASSIGN);
uc_compiler_set_jmpaddr(compiler, jmp_off, chunk->count);
}
static void
-uc_compiler_compile_nullish_common(uc_compiler_t *compiler, bool assignment, uc_value_t *var)
+uc_compiler_compile_nullish(uc_compiler_t *compiler)
{
uc_chunk_t *chunk = uc_compiler_current_chunk(compiler);
size_t jmpz_off, jmp_off;
- if (assignment)
- uc_compiler_emit_variable_copy(compiler, var);
-
- uc_compiler_emit_insn(compiler, 0, I_COPY);
- uc_compiler_emit_u8(compiler, 0, 0);
+ uc_compiler_emit_copy(compiler, 0, 0);
uc_compiler_emit_insn(compiler, 0, I_LNULL);
uc_compiler_emit_insn(compiler, 0, I_NES);
jmpz_off = uc_compiler_emit_jmpz(compiler, 0);
jmp_off = uc_compiler_emit_jmp(compiler, 0);
uc_compiler_set_jmpaddr(compiler, jmpz_off, chunk->count);
uc_compiler_emit_insn(compiler, 0, I_POP);
+ uc_compiler_parse_precedence(compiler, P_OR);
+ uc_compiler_set_jmpaddr(compiler, jmp_off, chunk->count);
+}
- if (assignment) {
- uc_compiler_parse_precedence(compiler, P_ASSIGN);
- uc_compiler_emit_variable_rw(compiler, var, TK_ASSIGN);
- }
- else {
- uc_compiler_parse_precedence(compiler, P_OR);
- }
+static void
+uc_compiler_compile_nullish_assignment(uc_compiler_t *compiler, uc_value_t *var)
+{
+ uc_chunk_t *chunk = uc_compiler_current_chunk(compiler);
+ size_t jmpz_off, jmp_off;
+ uc_compiler_emit_variable_copy(compiler, var);
+ uc_compiler_emit_insn(compiler, 0, I_LNULL);
+ uc_compiler_emit_insn(compiler, 0, I_NES);
+ jmpz_off = uc_compiler_emit_jmpz(compiler, 0);
+ uc_compiler_emit_variable_rw(compiler, var, 0);
+ jmp_off = uc_compiler_emit_jmp(compiler, 0);
+ uc_compiler_set_jmpaddr(compiler, jmpz_off, chunk->count);
+ uc_compiler_parse_precedence(compiler, P_ASSIGN);
+ uc_compiler_emit_variable_rw(compiler, var, TK_ASSIGN);
uc_compiler_set_jmpaddr(compiler, jmp_off, chunk->count);
}
@@ -1256,19 +1278,19 @@ uc_compiler_compile_assignment(uc_compiler_t *compiler, uc_value_t *var)
if (type == TK_ASNULLISH) {
uc_compiler_parse_advance(compiler);
- uc_compiler_compile_nullish_common(compiler, true, var);
+ uc_compiler_compile_nullish_assignment(compiler, var);
return true;
}
else if (type == TK_ASOR) {
uc_compiler_parse_advance(compiler);
- uc_compiler_compile_or_common(compiler, true, var);
+ uc_compiler_compile_or_assignment(compiler, var);
return true;
}
else if (type == TK_ASAND) {
uc_compiler_parse_advance(compiler);
- uc_compiler_compile_and_common(compiler, true, var);
+ uc_compiler_compile_and_assignment(compiler, var);
return true;
}
@@ -1853,24 +1875,6 @@ uc_compiler_compile_funcdecl(uc_compiler_t *compiler)
}
static void
-uc_compiler_compile_and(uc_compiler_t *compiler)
-{
- return uc_compiler_compile_and_common(compiler, false, NULL);
-}
-
-static void
-uc_compiler_compile_or(uc_compiler_t *compiler)
-{
- return uc_compiler_compile_or_common(compiler, false, NULL);
-}
-
-static void
-uc_compiler_compile_nullish(uc_compiler_t *compiler)
-{
- return uc_compiler_compile_nullish_common(compiler, false, NULL);
-}
-
-static void
uc_compiler_compile_dot(uc_compiler_t *compiler)
{
bool optional_chaining = (compiler->parser->prev.type == TK_QDOT);