Why are String Literals Immutable in C ?

Understanding the Immutability of String Literals in C

In C , string literals are known for their immutable nature and the consequences of attempting to modify them. This article delves into the reasons behind this property.

Firstly, string literals are placed in static memory, ensuring their existence throughout the program's execution. This enables compilers to store the literals in read-only memory sections for performance optimization.

Additionally, the immutability of string literals allows for efficient and consistent string management. To illustrate this, consider two string literals with the same ending:

<code class="c++">char *foo = "long string";
char *bar = "string";</code>

Compilers often merge these literals, with bar pointing to foo's ending segment. Modifying the contents of either literal could lead to unpredictable behavior in the merged string, making immutability essential for reliability.

Finally, the C standard committee recognized the widespread adoption of immutability optimizations by compilers. To avoid discrepancies and provide a clear definition, they specified that any attempt to modify a string literal should result in undefined behavior.

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