JPH113272A - Stack overflow detector - Google Patents

Abstract

(57) [Problem] To provide a stack overflow detection device capable of detecting and displaying that a stack has overflowed. SOLUTION: An LED display flag area is set in a shaded area near a boundary between a stack area SR and a variable area VR set in a RAM. When data is written to the LED display flag area, the LED is turned on. This makes it possible to detect and display that the stack area SR has overflowed. By the lighting of the LED, (a) indicates that the stack area SR is filled with data, (b) indicates that the stack area SR to which no data is written is remaining,
The case (c) indicates that the stack area has already overflowed, and the program variables and the like written in the variable area may have been lost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stack overflow detecting device for detecting that an amount of data written in a stack area allocated to a memory of a microcomputer (hereinafter referred to as "microcomputer") overflows the stack area. .

[0002]

2. Description of the Related Art Conventionally, when a microcomputer executes a predetermined processing program, a return address when a function or a subroutine is called is stored in a stack area secured in a part of a storage area of a memory. Is configured to be stored.

FIG. 6 is an explanatory diagram showing a storage area of a memory. In FIG. 6, a program area PR is a storage area in which a program executed by the microcomputer is stored, and a variable area VR is a storage area assigned to store variables of the program executed by the microcomputer. The stack area SR is a storage area allocated to store a return address when a function or a subroutine is called, and the like. The stack area SR is allocated from the memory address X to the last address FFFF.

Each time the microcomputer calls another function or subroutine based on the program being executed, the return address and the like are sequentially written into the stack area SR from the tail end of the stack area SR. . When the microcomputer reads a return address or the like from the stack area SR, the microcomputer sequentially reads data from the data stored in the stack area SR.

In such a stack operation, when the number of times data is written to the stack area SR is greater than the number of times data is read from the stack area SR, the usage rate of the stack area SR gradually increases. . Then, when further writing is performed, a stack overflow occurs, and data is written to the variable area VR and the program area PR on the head side of the address X.

However, if a return address or the like when a function or subroutine is called is written in the variable area VR or the program area PR, the variable or program stored in the variable area VR or the program area PR is overwritten. And the variable area VR and the program area P
R data is lost.

When the microcomputer reads and processes the lost data in the variable area VR and the program area PR, the data is not appropriate data, and the program runs away.

In order to prevent such a program runaway, it is sufficient to set a sufficient area as a stack area in advance, but increasing the memory capacity is not preferable because it increases the cost. Therefore, efficient use of the storage area of the memory is desired.

[0009]

In the stage of software development of a microcomputer, it is necessary to determine a suitable area as a stack area and set the stack area.

However, conventionally, it is difficult to know that the stack has overflowed, and it is difficult to know that the stack has overflowed until the program runs away.

Therefore, it takes a certain amount of time to confirm that the cause of the program runaway is the stack overflow. As a result, it takes time to optimize the stack area, and there is a problem that efficient software development cannot be performed.

The present invention has been made in view of the above problems, and has as its object to provide a stack overflow detection device capable of detecting and displaying that a stack has overflowed.

[0013]

According to a first aspect of the present invention, there is provided a storage means (13) which is readable / writable, and which has a predetermined access to the storage means (13). Arithmetic processing means (11) for executing the above processing
And a display means (20) whose display state is controlled by the arithmetic processing means (11), wherein the display area (20) is provided near a boundary between a stack area and a variable area set in a storage area of the storage means (13). And a processing unit (11) monitors the display state change area, and in response to a change in the storage state of the display state change area, the calculation processing unit (11) displays the display state (20). The display state is changed.

According to a second aspect of the present invention, in the device according to the first aspect, the monitoring of the display state change area performed by the arithmetic processing means (11) is periodically performed at predetermined time intervals. And

According to a third aspect of the present invention, in the device according to the first or second aspect, the display state change area is provided in the stack area.

According to a fourth aspect of the present invention, in the device according to the third aspect, the display state change area is provided in an area adjacent to the variable area.

According to a fifth aspect of the present invention, in the device according to the first or second aspect, the display state change area is provided in a variable area.

[0018]

In the above construction, the invention according to claim 1 is
Arithmetic processing means (11) in response to a change in the storage state of the display state change area so that the storage state of the display state change area can be visually recognized as being changed;
Changes the display state of the display means (20).

According to a second aspect of the present invention, the display state change area is periodically monitored by the arithmetic processing means (11) so that the display means (20) can perform display in real time. Operate.

According to the third aspect of the present invention, the display is performed by the display means (20) so as to notify that the stack area where no data is written is remaining.

According to the fourth aspect of the present invention, the display by the display means (20) is performed so as to notify that the stack area is filled with the data.

According to the fifth aspect of the present invention, the display means (20) informs that there is a possibility that the program variable or the like which has already overflowed the stack area and has been written in the variable area may be lost. Is displayed.

[0023]

FIG. 1 is a schematic diagram showing a configuration of a stack overflow detection device according to an embodiment of the present invention. As shown in FIG. 1, inside the microcomputer 10,
Arithmetic processing unit 11 for executing arithmetic processing by executing a program
A ROM (Read Only Memory) 12 which is a read-only memory for storing programs and the like in advance, and a RAM (Random Access Memory) which is a memory for temporarily storing data when the arithmetic processing unit 11 executes the program. Memor
y) 13 and an I / O port 14 for exchanging data with an external mechanism of the microcomputer 10 are provided.

At least one of the outputs obtained from the I / O port 14 is led to the LED display unit 20. A plurality of LED display units 20 may be provided. Then, the LED display unit 20 outputs an LED (Light Emitting Diode) 2 based on an output signal from the microcomputer 10.
1 is configured to emit light.

The microcomputer 10 and the LED 21 are mounted on at least one board to serve as a control board. This control board functions so as to control the entire product when completed as a product. The LED 21 functions as a display mechanism for indicating the operation status of the product and the like.
For example, when the product is an air conditioner, and the control board controls each mechanism of the air conditioner,
The LED 21 lights up according to the operation state of the air conditioner. When a plurality of LED display units 20 are provided, the operating state can be known in detail by the lighting pattern.

Such a control board is also used at the stage of software development of the microcomputer 10. And in this embodiment, at the software development stage,
The LED 21 functions as display means for notifying the developer that the stack area has overflowed.

On the other hand, in the microcomputer 10, the RAM 13
Is set in advance as a stack area. The LED is located near the boundary between the stack area of the storage area of the RAM 13 and the variable area which is the other storage area.
A display flag area is set in advance. And arithmetic processing unit 1
1 periodically detects whether or not data has been written to the LED display flag area, and if the data has been written, outputs a signal to the LED display unit 20 to cause the LED 21 to emit light. It is configured as follows.

FIG. 2 shows a RAM 1 according to this embodiment.
FIG. 9 is a diagram showing an LED display flag area set near a boundary between a stack area and a variable area set to 3; In FIG. 2, the area from the address X to the address FFFF of the RAM 13 is set as the stack area SR, the variable area VR is set at the head side of the stack area SR, and the head area is set at the top of the variable area VR. A program area PR is set on the side. And FIG.
Each shaded portion shown in (a) to (c) is an LED display flag area.

First, in FIG. 2A, the stack region SR
Is set as the LED display flag area. Then, when data is written to the LED display flag area, data is written to all of the stack areas SR. Therefore, when the LED display flag area is set as shown in FIG. 2A, when the LED 21 is turned on, it is understood that the stack area is filled with data.

Next, in FIG. 2B, the stack region SR
The flag area for LED display is set at the tail end side from the start address X set as (1). When data is written in the LED display flag area, data is written in many areas of the stack area SR, and the stack area in which no data is written remains small. Therefore,
When the LED display flag area is set as shown in FIG. 2B, when the LED 21 is turned on, it can be seen that the stack area where no data is written remains small.

Further, in FIG. 2C, the stack area S
An LED display flag area is set in the variable area VR on the head side of the head address X set as R. Then, when data is written to the LED display flag area, the stack area SR has already overflowed. Therefore, when the LED display flag area is set as shown in FIG.
When 21 is turned on, it is found that the stack area SR has already overflowed and the program variables and the like written in the variable area VR may have been lost.

Here, since the stack overflow detection device of this embodiment uses a control board which is originally used for a product, an L for displaying the operation status of the product is used.
In the software development stage, the ED display unit 20 is
Since it can function as a display unit for notifying the developer that the stack area has overflowed specially, there is no need to provide a display mechanism only for the software development stage, thereby enabling efficient software development. . Furthermore, since a program for displaying the operating status of the product can be used for the program for turning on the LED 21, it is not necessary to create a display program only for the software development stage, and the program is stored. It is not necessary to increase the storage capacity of the ROM 12 to be stored, and efficient development can be performed.

The processing of such a microcomputer will be described with reference to a flowchart.

FIG. 3 is a flowchart of a process performed by the arithmetic processing unit 11 of the microcomputer 4 according to this embodiment. First, when the process is started in step S1, a startup process is performed. The start-up process is a process for performing initial setting of a hardware mechanism (for example, the I / O port 14 and the like) inside the microcomputer 10. Next, in step S2, initialization of data, variables, and the like is performed. When the initialization is completed, the interrupt processing is permitted in step S3. After that, the arithmetic processing unit 11
Enters an infinite loop shown in step S4. Then, various types of interrupt processing are performed during the processing of the infinite loop shown in step S4. A priority level is set in the interrupt process according to the type of the process, and an interrupt process with a higher priority level may be further interrupted during execution of the interrupt process.
When the interrupt processing is performed as described above, the return address when the interrupt processing is completed is sequentially stored in the stack area. For example, when the control board is for controlling the air conditioner, the above-described interrupt processing includes processing such as heat exchange processing and defrosting processing.

The process for turning on the LED 21 is also executed as an interrupt process. FIG. 4 is a flowchart of a process for determining the lighting of the LED in this embodiment. This processing is executed by generating an interrupt at regular time intervals such as 10 ms. In step S11, it is detected whether or not data is set in all of the flag areas set for LED display. At this time, by simply setting the LED display flag area shown in FIG. 2 as the flag area set for the LED display, it is possible to recognize that the stack area is immediately before or immediately after the overflow. Can be. In step S12, based on the detected data, LED
Confirm the lighting pattern of. In step S13, a display variable is set in a predetermined storage area (for example, a variable area VR) according to the determined LED lighting pattern. This completes the interrupt process for determining the lighting of the LED. Since this process is a process executed by generating an interrupt at regular time intervals such as 10 ms, it is possible to detect in real time whether or not the LED should be turned on.

FIG. 5 is a flowchart of a process for turning on an LED in this embodiment. This process is also a process executed by generating an interrupt at regular time intervals such as 1 ms. Step S
At 21, the display variables set in the processing of FIG. 4 are read. In step S22, an output for lighting the LED 21 is performed from the I / O port 14 according to the LED lighting pattern indicated by the read display variable. Thus, the interrupt processing for lighting the LED ends.

The processes in the flowcharts shown in FIGS. 3, 4 and 5 are necessary processes for an actual product. Then, as described above, by simply adding the LED display flag area shown in FIG. 2 as an area for detecting whether or not data is set in step S11 shown in FIG. 4, the developer overflows the stack area. It can be recognized immediately before or immediately after. Therefore, it is possible to efficiently recognize that the stack has overflowed in real time without waiting for the program to run away. Further, since it is not necessary to create a program dedicated to the development stage, it is not necessary to increase the capacity of the ROM 12, and it is possible to improve the efficiency of software development.

By the way, it goes without saying that the display means for displaying that the stack has overflowed is not limited to the LED display, but may be any means that can be visually recognized.

The positional relationship between the stack area SR, the variable area VR, and the program area PR set in the RAM 13 is not limited to the positional relationship shown in FIG. , The program area PR may be set in this order, but even in such a case, if an LED display flag area is set near the boundary between the stack area SR and the variable area VR, the stack overflows. You can recognize that you have done.

[0040]

As described above, according to the first aspect of the present invention, the display state change area is provided near the boundary between the stack area and the variable area set in the storage area of the storage means (13). At the same time, the arithmetic processing means (11) monitors the display state change area, and the arithmetic processing means (11) changes the display state of the display means (20) in response to the change of the storage state of the display state change area. Therefore, it is possible to efficiently recognize that the stack has overflowed in real time without waiting for the program to run away. Further, since it is not necessary to create a program dedicated to the development stage, it is not necessary to increase the capacity of the ROM, and it is possible to improve the efficiency of software development.

According to the second aspect of the present invention, the monitoring of the display state change area performed by the arithmetic processing means (11) is periodically performed at predetermined time intervals. It is possible to detect whether or not to perform display.

According to the third aspect of the present invention, since the display state change area is provided in the stack area, the display means (2)
When the display according to 0) is performed, it can be seen that the stack area in which no data is written remains small.

According to the fourth aspect of the present invention, since the display state change area is provided in the area adjacent to the variable area, when the display is performed by the display means (20), the stack area is filled with data. I understand.

According to the fifth aspect of the present invention, since the display state change area is provided in the variable area, the display means (20)
Is displayed, it is found that the stack area has already overflowed, and the program variables and the like written in the variable area may have been lost.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a stack overflow detection device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an LED display flag area set near a boundary between a stack area and a variable area set in a RAM according to the embodiment of the present invention;

FIG. 3 is a flowchart of a process in an arithmetic processing unit of the microcomputer according to the embodiment.

FIG. 4 is a flowchart of a process for determining lighting of an LED according to the embodiment.

FIG. 5 is a flowchart of a process for turning on an LED according to the embodiment.

FIG. 6 is an explanatory diagram showing a storage area of a memory.

[Explanation of symbols]

10 microcomputer, 11 arithmetic processing unit, 12 ROM, 1
3 RAM, 14 I / O port, 20 LED display, 21 LED, VR variable area, SR stack area

Claims (5)

[Claims] A readable / writable storage means (1)
3), an arithmetic processing means (11) for accessing the storage means (13) and executing a predetermined process, and a display means (20) whose display state is controlled by the arithmetic processing means (11). A display state change area is provided near a boundary between a stack area and a variable area set in a storage area of the storage means (13), and the arithmetic processing means (11) provides the display state change area. A state change area is monitored, and in response to a change in the storage state of the display state change area, the arithmetic processing means (11) causes the display means (2
A stack overflow detection device, wherein the display state of 0) is changed. 2. The apparatus according to claim 1, wherein the monitoring of the display state change area performed by the arithmetic processing means (11) is performed periodically at predetermined time intervals. apparatus. 3. The stack overflow detecting device according to claim 1, wherein the display state change area is provided in the stack area. 4. The device according to claim 3, wherein the display state change area is provided in an area adjacent to the variable area. 5. The stack overflow detection device according to claim 1, wherein the display state change area is provided in the variable area.