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Use automatic allocation for RPN stack

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This commit is contained in:
Rangi42
2024-02-22 21:36:38 -05:00
committed by Sylvie
parent 843f3394c8
commit a5ea25cde5
2 changed files with 16 additions and 68 deletions
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82
src/link/patch.cpp
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@@ -17,58 +17,16 @@
#include "opmath.hpp"
#include "platform.hpp"
/*
* This is an "empty"-type stack. Apart from the actual values, we also remember
* whether the value is a placeholder inserted for error recovery. This allows
* us to avoid cascading errors.
*
* The best way to think about this is a stack of (value, errorFlag) pairs.
* They are only separated for reasons of memory efficiency.
*/
struct RPNStack {
int32_t *values;
bool *errorFlags;
size_t size;
size_t capacity;
} stack;
struct RPNStackEntry {
int32_t value;
bool errorFlag; // Whether the value is a placeholder inserted for error recovery
};
static void initRPNStack(void)
{
stack.capacity = 64;
stack.values = (int32_t *)malloc(sizeof(*stack.values) * stack.capacity);
stack.errorFlags = (bool *)malloc(sizeof(*stack.errorFlags) * stack.capacity);
if (!stack.values || !stack.errorFlags)
err("Failed to init RPN stack");
}
static void clearRPNStack(void)
{
stack.size = 0;
}
std::deque<struct RPNStackEntry> rpnStack;
static void pushRPN(int32_t value, bool comesFromError)
{
if (stack.size >= stack.capacity) {
static const size_t increase_factor = 2;
if (stack.capacity > SIZE_MAX / increase_factor)
errx("Overflow in RPN stack resize");
stack.capacity *= increase_factor;
stack.values =
(int32_t *)realloc(stack.values, sizeof(*stack.values) * stack.capacity);
stack.errorFlags =
(bool *)realloc(stack.errorFlags, sizeof(*stack.errorFlags) * stack.capacity);
// Static analysis tools complain that the capacity might become
// zero due to overflow, but fail to realize that it's caught by
// the overflow check above. Hence the stringent check below.
if (!stack.values || !stack.errorFlags || !stack.capacity)
err("Failed to resize RPN stack");
}
stack.values[stack.size] = value;
stack.errorFlags[stack.size] = comesFromError;
stack.size++;
rpnStack.push_front({ .value = value, .errorFlag = comesFromError });
}
// This flag tracks whether the RPN op that is currently being evaluated
@@ -77,18 +35,14 @@ static bool isError = false;
static int32_t popRPN(struct FileStackNode const *node, uint32_t lineNo)
{
if (stack.size == 0)
if (rpnStack.empty())
fatal(node, lineNo, "Internal error, RPN stack empty");
stack.size--;
isError |= stack.errorFlags[stack.size];
return stack.values[stack.size];
}
struct RPNStackEntry entry = rpnStack.front();
static void freeRPNStack(void)
{
free(stack.values);
free(stack.errorFlags);
rpnStack.pop_front();
isError |= entry.errorFlag;
return entry.value;
}
// RPN operators
@@ -132,7 +86,7 @@ static int32_t computeRPNExpr(struct Patch const *patch,
uint8_t const *expression = patch->rpnExpression;
int32_t size = patch->rpnSize;
clearRPNStack();
rpnStack.clear();
while (size > 0) {
enum RPNCommand command = (enum RPNCommand)getRPNByte(&expression, &size,
@@ -142,7 +96,7 @@ static int32_t computeRPNExpr(struct Patch const *patch,
isError = false;
// Be VERY careful with two `popRPN` in the same expression.
// C does not guarantee order of evaluation of operands!
// C++ does not guarantee order of evaluation of operands!
// So, if there are two `popRPN` in the same expression, make
// sure the operation is commutative.
switch (command) {
@@ -447,9 +401,9 @@ static int32_t computeRPNExpr(struct Patch const *patch,
pushRPN(value, isError);
}
if (stack.size > 1)
if (rpnStack.size() > 1)
error(patch->src, patch->lineNo,
"RPN stack has %zu entries on exit, not 1", stack.size);
"RPN stack has %zu entries on exit, not 1", rpnStack.size());
isError = false;
return popRPN();
@@ -460,7 +414,6 @@ static int32_t computeRPNExpr(struct Patch const *patch,
void patch_CheckAssertions(std::deque<struct Assertion> &assertions)
{
verbosePrint("Checking assertions...\n");
initRPNStack();
for (struct Assertion &assert : assertions) {
int32_t value = computeRPNExpr(&assert.patch,
@@ -491,8 +444,6 @@ void patch_CheckAssertions(std::deque<struct Assertion> &assertions)
assert.message);
}
}
freeRPNStack();
}
/*
@@ -563,8 +514,5 @@ static void applyPatches(struct Section *section)
void patch_ApplyPatches(void)
{
initRPNStack();
sect_ForEach(applyPatches);
freeRPNStack();
}