fscanf stops working after sometimes

Question

the works fine for the starting few lines then stops working.

while(!feof(fp)){



    char cc=fgetc(fp);fputc(cc,o);putchar(cc);

    if(cc==EOF)break;
    if(cc=='\n'){
    char aa=fgetc(fp);
    fseek(fp,-1,SEEK_CUR);

    if(aa==' '){

    fscanf(fp,"%s",&mne);
    fprintf(o,"\t%s\t",mne);
    printf("\t%s\t",mne);

    if(!strcmp(mne,"RSUB")){strcat(objectCode[count].n,get_opcode(mne));
                            printf("%s\n",objectCode[count].n);count++;
                            continue;}
    fscanf(fp,"%s",&var);
    fprintf(o,"%s",var);
    printf("%s\t",var);

    char buff[10];
    strcat(objectCode[count].n,get_opcode(mne));
    sprintf(buff,"%0X",get_add(var));
    strcat(objectCode[count].n,buff);
    fprintf(o,"%s\n",objectCode[count].n);
    printf("%s\n",objectCode[count].n);
    count++;
    continue;
    }
    cout<<"\nno tabs\n";


            **fscanf(fp,"%s%s%s",&a,&mne,&var);**
            fprintf(o,"%s\t%s\t%s",a,mne,var);
            printf("%s\t%s\t%s\t",a,mne,var);

            if(!strcmp(mne,"BYTE"))
            {
                    char buff[4];
                    for(int i=2;i<(strlen(var)-1);i++)
                    {
                            sprintf(buff,"%0X",(int)var[i]);
                            strcat(objectCode[count].n,buff);

                    }
                    fprintf(o,"%s\n",objectCode[count].n);
                    printf("%s\n",objectCode[count].n);
                    count++;
                    continue;


            }
            else if(!strcmp(mne,"WORD"))
            {
                    char buff[10];
                    sprintf(buff,"%d",get_add(var));
                    strcat(objectCode[count].n,buff);
                    fprintf(o,"%s\n",objectCode[count].n);
                    printf("%s\n",objectCode[count].n);
                    count++; continue;
            }
            else if(!strcmp(mne,"RESW"))
            {
                    strcat(objectCode[count].n,"------");
                    fprintf(o,"%s\n",objectCode[count].n);
                    printf("%s\n",objectCode[count].n);
            }

            else if(!strcmp(mne,"RESB"))
            {
                    strcat(objectCode[count].n,"------");
                    fprintf(o,"\t%s\n",objectCode[count].n);
                    printf("%s\n",objectCode[count].n);
            }

            else
            {
                    char buff[10];
                    strcat(objectCode[count].n,get_opcode(mne));
                    sprintf(buff,"%0X",get_add(var));
                    strcat(objectCode[count].n,buff);
                    fprintf(o,"%s\n",objectCode[count].n);
                    printf("%s\n",objectCode[count].n);
            }
    count++;
    }

}

i am trying to read the following content from a file and generate the opcode.

    COPY    START   1000
FIRST   STL     RETADR
CLOOP   JSUB    RDREC
        LDA     LENGTH
        COMP    ZERO
        JEQ     ENDFIL
        JSUB    WRREC
        J       CLOOP
ENDFIL  LDA     EOF
        STA     BUFFER
        LDA     THREE
        STA     LENGTH
        JSUB    WRREC
        LDL     RETADR
        RSUB
EOF     BYTE    C'EOF'
THREE   WORD    3
ZERO    WORD    0
RETADR  RESW    1
LENGTH  RESW    1
BUFFER  RESB    4096

RDREC   LDX     ZERO
        LDA     ZERO
RLOOP   TD      INPUT
        JEQ     RLOOP
        RD      INPUT
        COMP    ZERO
        JEQ     EXIT
        STCH    BUFFER,X
        TIX     MAXLEN
        JLT     RLOOP
EXIT    STX     LENGTH
        RSUB
INPUT   BYTE    X'F1'
MAXLEN  WORD    4096

WRREC   LDX     ZERO
WLOOP   TD      OUTPUT
        JEQ     WLOOP
        LDCH    BUFFER,X
        WD      OUTPUT
        TIX     LENGTH
        JLT     WLOOP
        RSUB
OUTPUT  BYTE    X'05'
        END     FIRST

works fine till this line: EOF BYTE C'EOF' i tried indicators, it does enter the loop after this line but does not work from the fscanf line: fscanf(fp,"%s%s%s",&a,&mne,&var);

then goes into a deadlock. the fscanf stops working. please help.what might be the issue?

Answer 1

One issue that is a thorn is the optional label.

Most lines are of the format:

<optional-label> <instruction> <operands>  

Since each instruction is on a separate line, reading the file line by line and parsing the line seem to be the best issue here (as opposed to a more free form language like C++).

So we start with the fundamental program:

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>

void Process_Text_Line(const std::string& text_line)
{
   std::cout << text_line << "\n";
}

int main()
{
  std::ifstream program_file("my_program.asm");
  std::string text_line;
  while (std::getline(program_file, text_line);
  {
     // For now, echo the instruction
     Process_Text(text_line);
  }
  return EXIT_SUCCESS;
}

Get this working.

Next step, add more content to the Process_Text_Line method, such as recognition of labels, instructions and operands:

#include <vector>

void Process_Text_Line(const std::string& text_line)
{
   std::vector<std::string> instructions =
     {
        "STL", "JSUB",
        //...
     };

   // Extract the first "word".
   std::istringstream instruction_stream(text_line);
   std::string word;
   instruction_stream >> word;

   // If the word is not an instruction, consider it a label.
   std::string label;
   std::string opcode;
   if (std::find(instructions.begin(), instructions.end(), word) != instructons.end())
   {
      label = word;
      instruction_stream >> opcode;
   }
   else
   {
     opcode = word;
   }
   // Extract the operand
   std::string operand;
   instruction_stream >> operand;
   // Now print them:  
   std::cout << "Label: " << label;
   std::cout << ",  opcode: " << opcode;
   std::cout << ",  operand: " << operand << "\n";
   }

Once the label, opcode and operand are extracted, processing them is straight forward. There may be exceptions, where an opcode has more than one operand or zero operands.

One nice issue about using C++ streams and strings is that variable length records can be handled simply. For example, if an opcode has no operand, the extraction will generate an error, but processing continues. No worrying about whether or not to supply one, two or three format specifiers or arguments to scanf.