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size_t len;
char cstr[] = "char string";
signed char scstr[] = "signed char string";
unsigned char ucstr[] = "unsigned char string";

len = strlen(cstr);
len = strlen(scstr);  /* warns when char is unsigned */
len = strlen(ucstr);  /* warns when char is signed */

Wiki MarkupCompiling at high warning levels in compliance with guideline [recommendation MSC00-C. Compile cleanly at high warning levels] causes warnings to be issued when when

• Wiki Markup
  converting from {{unsigned char\[\]}} to {{const char *}} when {{char}} is signed

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  converting from {{signed char\[\]}} to {{const char *}} when {{char}} is defined to be unsigned

. Casts are required to eliminate these warnings, but excessive casts can make code difficult to read and hide legitimate warning messages.

If this C code were compiled using a C+\+ compiler, conversions from {{unsigned char\[\]}} to {{const char *}} and from {{signed char\[\]}} to {{const char *}} would be flagged as errors requiring casts.

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

Related Guidelines

CERT C++ Secure Coding Standard: STR04-CPP. Use plain char for characters in the basic character set

Bibliography

unmigrated-wiki-markup

\[[ISO/IEC 9899:1999|AA. Bibliography#ISO/IEC 9899-1999]\] Section 6.2.5, "Types" \[[MISRA 2004|AA. Bibliography#MISRA 04]\] Rule

MISRA Rule 6.1, "The plain char type shall be used only for the storage and use of character values"

Bibliography

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STR03-C. Do not inadvertently truncate a null-terminated byte string      07. Characters and Strings (STR)