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fix: add iteration limits to prevent parser hangs (fixes #2451) #2483

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Merged
krystophny merged 1 commit into from
Nov 23, 2025
Merged

fix: add iteration limits to prevent parser hangs (fixes #2451) #2483

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36 changes: 23 additions & 13 deletions src/parser/expressions/parser_expression_arrays.f90
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Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,7 @@ function parse_simple_array_elements(parser, arena, terminator, style, &
element_count = 0
allocate (temp_indices(20))

do
do while (element_count < 100000)
element_count = element_count + 1
if (element_count > size(temp_indices)) then
block
Expand Down Expand Up @@ -271,16 +271,22 @@ recursive function parse_modern_array_literal(parser, arena, start_token, &
spec_token = parser%consume()
type_spec_text = trim(type_spec_text) // spec_token%text
paren_depth = 1
do while (paren_depth > 0)
peek_token = parser%peek()
if (peek_token%text == "(") then
paren_depth = paren_depth + 1
else if (peek_token%text == ")") then
paren_depth = paren_depth - 1
end if
spec_token = parser%consume()
type_spec_text = type_spec_text // spec_token%text
end do
block
integer :: paren_count
integer, parameter :: MAX_PAREN_DEPTH = 1000
paren_count = 0
do while (paren_depth > 0 .and. paren_count < MAX_PAREN_DEPTH)
paren_count = paren_count + 1
peek_token = parser%peek()
if (peek_token%text == "(") then
paren_depth = paren_depth + 1
else if (peek_token%text == ")") then
paren_depth = paren_depth - 1
end if
spec_token = parser%consume()
type_spec_text = type_spec_text // spec_token%text
end do
end block
peek_token = parser%peek()
end if

Expand All @@ -301,7 +307,7 @@ recursive function parse_modern_array_literal(parser, arena, start_token, &
end if
end if

do
do while (element_count < 100000)
! Skip newlines and comments inside array literals
do
peek_token = parser%peek()
Expand Down Expand Up @@ -787,6 +793,8 @@ subroutine collect_index_arguments(parser, arena, helpers, closing_char, &
type(token_t), intent(out) :: close_token
type(token_t) :: token
integer :: arg_index
integer :: arg_count
integer, parameter :: MAX_ARGUMENTS = 10000

if (parser%is_at_end()) then
close_token = parser%peek()
Expand All @@ -799,8 +807,10 @@ subroutine collect_index_arguments(parser, arena, helpers, closing_char, &
if (arg_index > 0) then
allocate (arg_indices(1))
arg_indices(1) = arg_index
arg_count = 1

do
do while (arg_count < MAX_ARGUMENTS)
arg_count = arg_count + 1
token = parser%peek()
if (token%kind /= TK_OPERATOR .or. token%text /= ",") exit
token = parser%consume()
Expand Down
6 changes: 5 additions & 1 deletion src/parser/expressions/parser_expressions.f90
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Expand Up @@ -443,15 +443,19 @@ recursive function parse_expression_with_precedence(parser, arena, &
type(token_view_t) :: view
logical :: expect_operand, should_exit
type(token_t) :: token
integer :: iteration_count
integer, parameter :: MAX_ITERATIONS = 100000

call operator_stack_clear(operators)
call operand_stack_clear(operands)
call token_stack_clear(prefix_stack)
call build_token_view(view, parser)
expr_index = 0
expect_operand = .true.
iteration_count = 0

main_loop: do while (.true.)
main_loop: do while (iteration_count < MAX_ITERATIONS)
iteration_count = iteration_count + 1
token = view_peek_token(view, parser)
if (token%kind == TK_EOF) exit main_loop

Expand Down
106 changes: 106 additions & 0 deletions test/test_parser_iteration_limits.f90
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@@ -0,0 +1,106 @@
program test_parser_iteration_limits
use transformation_api, only: transform_lazy_fortran_string
implicit none

integer :: test_count, pass_count

test_count = 0
pass_count = 0

print *, "=== Parser Iteration Limit Tests (Issue #2451) ==="
print *

call test_complex_nested_calls()
call test_many_function_arguments()
call test_large_array_literal()

print *
print *, "=== Summary ==="
print *, "Tests run: ", test_count
print *, "Tests passed:", pass_count

if (pass_count == test_count) then
print *, "All parser iteration limit tests passed!"
else
print *, "FAILURE: Some tests failed"
stop 1
end if

contains

subroutine test_complex_nested_calls()
character(len=:), allocatable :: source, result, error_msg

test_count = test_count + 1
print *, "Testing complex nested function calls..."

source = "program test" // new_line('a') // &
" implicit none" // new_line('a') // &
" integer :: arr(3,3), res(2)" // new_line('a') // &
" arr = reshape([1,2,3,4,5,6,7,8,9], [3,3])" // new_line('a') // &
" res = maxloc(arr, dim=1, mask=arr > 5)" // new_line('a') // &
" print *, res" // new_line('a') // &
"end program test"

call transform_lazy_fortran_string(source, result, error_msg)

if (len_trim(result) > 0) then
print *, " PASS: Complex nested calls parsed without hang"
pass_count = pass_count + 1
else
print *, " FAIL: Parser failed on complex nested calls"
if (allocated(error_msg)) print *, " Error: ", trim(error_msg)
end if
end subroutine test_complex_nested_calls

subroutine test_many_function_arguments()
character(len=:), allocatable :: source, result, error_msg

test_count = test_count + 1
print *, "Testing function with many arguments..."

source = "program test" // new_line('a') // &
" implicit none" // new_line('a') // &
" call sub(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20)" // &
new_line('a') // &
"end program test"

call transform_lazy_fortran_string(source, result, error_msg)

if (len_trim(result) > 0) then
print *, " PASS: Many arguments parsed without hang"
pass_count = pass_count + 1
else
print *, " FAIL: Parser failed on many arguments"
if (allocated(error_msg)) print *, " Error: ", trim(error_msg)
end if
end subroutine test_many_function_arguments

subroutine test_large_array_literal()
character(len=:), allocatable :: source, result, error_msg

test_count = test_count + 1
print *, "Testing large array literal..."

source = "program test" // new_line('a') // &
" implicit none" // new_line('a') // &
" integer :: x(50)" // new_line('a') // &
" x = [1,2,3,4,5,6,7,8,9,10," // &
"11,12,13,14,15,16,17,18,19,20," // &
"21,22,23,24,25,26,27,28,29,30," // &
"31,32,33,34,35,36,37,38,39,40," // &
"41,42,43,44,45,46,47,48,49,50]" // new_line('a') // &
"end program test"

call transform_lazy_fortran_string(source, result, error_msg)

if (len_trim(result) > 0) then
print *, " PASS: Large array literal parsed without hang"
pass_count = pass_count + 1
else
print *, " FAIL: Parser failed on large array literal"
if (allocated(error_msg)) print *, " Error: ", trim(error_msg)
end if
end subroutine test_large_array_literal

end program test_parser_iteration_limits