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fix: escape trigraphs in C and C++ string literals [patch] - #164
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C up to C17, and C++ before C++17, replace trigraphs such as ??! and ??/ inside string literals, so "what??!" compiled with -std=c11 printed what| and ??/ became a backslash escaping the next character. CFamilyGenerator now overrides EscapeString to write the second ? of every ?? pair as \?, which is a question mark in every C and C++ standard and breaks every trigraph without touching a lone ?. EscapeString becomes virtual for this; the other languages keep the shared escaping, since \? is not an escape in Go, Rust or JavaScript. Fixes #107 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01NfxXtpcxX8hkLYrePfHkV4
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Fixes #107
What was wrong
C up to C17, and C++ before C++17, replace trigraphs inside string literals.
"what??!"compiled withgcc -std=c11printedwhat|.??/became a backslash that escaped the next character, which could swallow the closing quote.Change
CFamilyGeneratornow overridesEscapeString. After the shared escaping, it writes the second?of every??pair as\?.\?is a question mark in every C and C++ standard, so the string's value doesn't change.???!becomes?\?\?!.?(for example"ok?") is written as it was.LanguageGeneratorBase.EscapeStringis nowprotected virtualso the C family can override it.\?is not an escape in Go, Rust or JavaScript.EscapeString, so they are covered too.Tests
New file:
Coder.Test/Languages/StringLiteralTrigraphTests.cs.CFamilyBreaksEveryTrigraph(C and C++): pins the exact literal written for every trigraph, a???!run and a lone?, and asserts that no??is left.OtherLanguagesWriteQuestionMarksAsIs(C#, JavaScript, Python, Go and Rust): question marks are written unchanged.CompiledWithTrigraphsOn_TheStringsKeepTheirValue:"what??!"and"a??/b".-std=c11 -Wall -Wextra -pedantic -Werror=trigraphsand runs it.ToolchainHarnessas the existing compile tests, and is inconclusive when no C compiler is on the path.With the
CFamilyGeneratorchange reverted, three tests fail: bothCFamilyBreaksEveryTrigraphrows and the compile-and-run test. The full suite passes: 1070 passed, 0 skipped.🤖 Generated with Claude Code
https://claude.ai/code/session_01NfxXtpcxX8hkLYrePfHkV4
Generated by Claude Code