https://gcc.gnu.org/g:1297b7204aca7fbad741ae02086fa5e134083a5f
commit r16-7173-g1297b7204aca7fbad741ae02086fa5e134083a5f Author: Jakub Jelinek <[email protected]> Date: Fri Jan 30 10:56:10 2026 +0100 libcpp: Fix up comment handling in -fdirectives-only preprocessing [PR123273] Back in 2020 Nathan rewrote the -E -fdirectives-only preprocessing. In PR103130 a year and half later I've fixed the handling of comments so that /* \*/ is considered as full comment even when * is escaped, to match the normal preprocessing. The following testcases shows further bugs in the comment handling. One is that /* *\/ should not be considered as full comment (i.e. when the / after * is escaped). And another one is that the code was treating any number of backslashes as escape, which is wrong, only a single backslash is an escape, two backslashes preprocess as one backslash, three as one backslash and one escape, etc. So, while /* *\ / is a full comment, /* *\\ / or /* *\\\\\\\\\\\\\ / is not. 2026-01-30 Jakub Jelinek <[email protected]> PR preprocessor/123273 * lex.cc (cpp_directive_only_process): Only go to done_comment for '/' if star is true and esc is false. When seeing '\\' with esc set to true, clear esc as well as star instead of keeping esc set. * c-c++-common/cpp/dir-only-10.c: New test. * c-c++-common/cpp/dir-only-11.c: New test. Diff: --- gcc/testsuite/c-c++-common/cpp/dir-only-10.c | 5 +++++ gcc/testsuite/c-c++-common/cpp/dir-only-11.c | 6 ++++++ libcpp/lex.cc | 10 ++++++++-- 3 files changed, 19 insertions(+), 2 deletions(-) diff --git a/gcc/testsuite/c-c++-common/cpp/dir-only-10.c b/gcc/testsuite/c-c++-common/cpp/dir-only-10.c new file mode 100644 index 000000000000..902d378fd3a2 --- /dev/null +++ b/gcc/testsuite/c-c++-common/cpp/dir-only-10.c @@ -0,0 +1,5 @@ +/* PR preprocessor/123273 */ +/* { dg-do preprocess } */ +/* { dg-options -fdirectives-only } */ + +/* *\/""" */ diff --git a/gcc/testsuite/c-c++-common/cpp/dir-only-11.c b/gcc/testsuite/c-c++-common/cpp/dir-only-11.c new file mode 100644 index 000000000000..33437bd508cb --- /dev/null +++ b/gcc/testsuite/c-c++-common/cpp/dir-only-11.c @@ -0,0 +1,6 @@ +/* PR preprocessor/123273 */ +/* { dg-do preprocess } */ +/* { dg-options -fdirectives-only } */ + +/* *\\ +/""" */ diff --git a/libcpp/lex.cc b/libcpp/lex.cc index df278534eeee..63f7a5fe5b8a 100644 --- a/libcpp/lex.cc +++ b/libcpp/lex.cc @@ -5490,7 +5490,13 @@ cpp_directive_only_process (cpp_reader *pfile, switch (c) { case '\\': - esc = true; + if (esc) + { + star = false; + esc = false; + } + else + esc = true; break; case '\r': @@ -5521,7 +5527,7 @@ cpp_directive_only_process (cpp_reader *pfile, break; case '/': - if (star) + if (star && !esc) goto done_comment; /* FALLTHROUGH */
