How Does GCC Find Header Files Without Explicit Paths?

Unveiling GCC's Default Include Directory Secrets

When compiling with GCC, the preprocessor effortlessly locates essential include files like stdio and stdlib without explicit path specifications. How does this magic happen?

The key lies in examining GCC's default paths and their priorities. To uncover these secrets, employ the following commands:

For C:

echo | gcc -xc -E -v -

For C :

echo | gcc -xc++ -E -v -

Decoding the Flags:

• -x specifies the language (C or C )
• -E triggers preprocessor-only execution
• -v verbosely prints executed commands
• - feeds an empty string to preprocess via stdin

By feeding an empty string to the preprocessor, we effectively preprocess a non-existent file generated on the fly.

Prioritizing Default Directories:

The output of these commands reveals a prioritized list of default include directories that GCC searches. This information empowers you to understand and modify include paths as needed.

For further clarity, refer to this insightful article: https://explainshell.com/explain?cmd=echo | gcc -xc -E -v -

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