Joseph Myers
3e3fdf3d52
The libcpp function cpp_avoid_paste is used to insert whitespace in preprocessed output where needed to avoid two consecutive preprocessing tokens, that logically (e.g. when stringized) do not have whitespace between them, from being incorrectly lexed as one when the preprocessed input is reread by a compiler. This fails to allow for digit separators, so meaning that invalid code, that has a CPP_NUMBER (from a macro expansion) followed by a character literal, can result in preprocessed output with a valid use of digit separators, so that required syntax errors do not occur when compiling with -save-temps. Fix this by handling that case in cpp_avoid_paste (as with other cases in cpp_avoid_paste, this doesn't try to check whether the language version in use supports digit separators; it's always OK to have unnecessary whitespace in preprocessed output). Note: there are other cases, with various kinds of wide character or string literal following a CPP_NUMBER, where spurious pasting of preprocessing tokens can occur but the sequence of tokens remains invalid both before and after that pasting. Maybe cpp_avoid_paste should also handle those cases (and similar cases after a CPP_NAME), to ensure the sequence of preprocessing tokens in preprocessed output is exactly right, whether or not it affects whether syntax errors occur. This patch only addresses the case with digit separators where invalid code can fail to be diagnosed without the space inserted. Bootstrapped with no regressions for x86_64-pc-linux-gnu. libcpp/ * lex.c (cpp_avoid_paste): Do not allow pasting CPP_NUMBER with CPP_CHAR. gcc/testsuite/ * g++.dg/cpp1y/digit-sep-paste.C, gcc.dg/c2x-digit-separators-3.c: New tests.
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