Symptom#

A test that embeds a query or regex in a raw string literal fails to compile with a burst of unrelated-looking errors:

test_prefilter.cpp:43:37: error: expected '}'
test_prefilter.cpp:43:44: error: use of undeclared identifier 'name'
test_prefilter.cpp:43:59: warning: missing terminating '"' character [-Winvalid-pp-token]

The line was:

R"(name ~ "(cuda|hip)")"

Cause#

R"(...)" ends at the first )" in the text. A pattern whose last character before its closing quote is ) (a group at the end: "(cuda|hip)", "a(?=b)", extract(p, "run_([0-9]+)", 1)) contains )" and ends the literal early.

Fix#

Give such literals a delimiter that cannot occur in the text:

R"q(name ~ "(cuda|hip)")q"

Use it for every literal that holds a regex or a group, not only the ones that fail today.

Evidence#

• dftracer-utils tests/index/test_prefilter.cpp and tests/duql/test_patterns.cpp (2026-09-28): 11 literals with regex groups failed to compile as R"(...)" and compiled and passed as R"q(...)q".