Implement preprocessor directive #ifndef #158
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Previously in PR sysprog21#158, #ifndef is not sufficient enough to address optional file inclusion issue in shecc, since shecc currently includes file before tokenization / parsing pass. Therefore, "#pragma once" is the only way to prevent recursively file inclusion. Although "#pragma once" is not standard anywhere in C standards, major C compilers such as GCC and Clang do support this preprocessor directive.
ChAoSUnItY
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Apr 17, 2025
Previously in PR sysprog21#158, #ifndef is not sufficient enough to address optional file inclusion issue in shecc, since shecc currently includes file before tokenization / parsing pass. Therefore, "#pragma once" is the only way to prevent recursively file inclusion. Although "#pragma once" is not standard anywhere in C standards, major C compilers such as GCC and Clang do support this preprocessor directive.
ChAoSUnItY
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Apr 17, 2025
Previously in PR sysprog21#158, #ifndef is not sufficient enough to address optional file inclusion issue in shecc, since shecc currently includes file before tokenization / parsing pass. Therefore, "#pragma once" is the only way to prevent recursively file inclusion. Although "#pragma once" is not standard anywhere in C standards, major C compilers such as GCC and Clang do support this preprocessor directive.
ChAoSUnItY
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Apr 19, 2025
Previously in PR sysprog21#158, #ifndef is not sufficient enough to address optional file inclusion issue in shecc, since shecc currently includes file before tokenization / parsing pass. Therefore, "#pragma once" is the only way to prevent recursively file inclusion. Although "#pragma once" is not standard anywhere in C standards, major C compilers such as GCC and Clang do support this preprocessor directive.
ChAoSUnItY
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Apr 22, 2025
Previously in PR sysprog21#158, #ifndef is not sufficient enough to address optional file inclusion issue in shecc, since shecc currently includes file before tokenization / parsing pass. Therefore, "#pragma once" is the only way to prevent recursively file inclusion. Although "#pragma once" is not standard anywhere in C standards, major C compilers such as GCC and Clang do support this preprocessor directive.
ChAoSUnItY
added a commit
to ChAoSUnItY/shecc
that referenced
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Apr 22, 2025
Previously in PR sysprog21#158, #ifndef is not sufficient enough to address optional file inclusion issue in shecc, since shecc currently includes file before tokenization / parsing pass. Therefore, "#pragma once" is the only way to prevent recursively file inclusion. Although "#pragma once" is not standard anywhere in C standards, major C compilers such as GCC and Clang do support this preprocessor directive.
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To prevent redefinition or serving other purposes, we sometimes need to negate the result of
defined, however, currently shecc does support neither negation operator in macro scope, e.g.!defined(SOME_MACRO), nor#ifndef. Thus, in this PR, we introduce preprocessor directive#ifndefto solve this issue without massively refactoring frontend codebase (since frontend refactoring is WIP).