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The atof, atoi, atol, and atoll functions are obsolete because the strod, strtof, strtol, strtold, strtoll, strotul, and strtoull functions can emulate their usage and have more robust error-handling capabilities. See INT05-C. Do not use input functions to convert character data if they cannot handle all possible inputs.

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The asctime and ctime functions are obsolete because they use non-reentrant static buffers and can be emulated using asctime_s and ctime_s.

Unchecked Obsolete Functions

The following are hereby defined to be unchecked obsolete functions:

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Noncompliant Code Example

In this noncompliant code example, the obsolete functions strcat and strcpy are used.

void complain(const char *msg) {
  static const char prefix[] = "Error: ";
  static const char suffix[] = "\n";
  char buf[BUFSIZE];

  strcpy(buf, prefix);
  strcat(buf, msg);
  strcat(buf, suffix);
  fputs(buf, stderr);
}
 

Compliant Solution

In this compliant solution, strcat() and strcpy() are replaced by strcat_s() and strcpy_s().

enum { BUFFERSIZE=256 };

void complain(const char *msg) {
  static const char prefix[] = "Error: ";
  static const char suffix[] = "\n";
  char buf[BUFFERSIZE];

  strcpy_s(buf, BUFFERSIZE, prefix);
  strcat_s(buf, BUFFERSIZE, msg);
  strcat_s(buf, BUFFERSIZE, suffix);
  fputs(buf, stderr);
}

Noncompliant Code Example

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FILE *file;
/* Setup file */
setbuf(file, NULL);
/* ... */
 

Compliant Solution

In this compliant solution.

Noncompliant Code Example

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char file_name[L_tmpnam];
FILE *fp;

if (!tmpnam(file_name)) {
  /* Handle error */
}

/* A TOCTOU race condition exists here */

fp = fopen(file_name, "wb+");
if (fp == NULL) {
   /* Handle error */
}
 

Compliant Solution

In this compliant solution.

Noncompliant Code Example

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In this compliant solution.,

Exceptions

MSC34-EX1: If an out-of-bounds store cannot occur in a specific invocation of a function, the invocation of that function is permitted by this rule. The rationale for this exception is that the simple use of such a function in a program does not mean the program is incorrect.   A requirement to To eliminate the use of such a function requires that , the programmer must replace calls to the deprecated or obsolete function with  with calls to the alternative functions.   Unfortunately, the process of modifying existing code frequently introduces defects and vulnerabilities and is not recommended.   New code should be developed in conformance to this guideline, however.

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Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

ISO/IEC 9945:2003

ISO/IEC 9899:2011 Section 7.21.3, "Files," Section 7.21.4, "Operations on files," Section 7.21.5.5, "The setbuf function," Section 7.21.6, "Formatted input/output functions," 7.21.9.2, "The fseek function"; 7.21.9.5, "The rewind function," Section 7.22.1.4, "The strtol, strtoll, strtoul, and strtoull functions," 7.24, "String handling <string.h>," and Section 7.24.5.8, "The strtok function"

ISO/IEC 23360-1:2006

ISO/IEC TR 24731-1:2007

ISO/IEC JTC1/SC22/WG11 Rationale for TR 24731 Extensions to the C Library Part I: Bounds-checking interfaces

ISO/IEC TR 24772 "TRJ Use of libraries"

ISO/IEC PDTR 24731-2

MISRA Rule 20.4

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Bibliography

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