diff --git a/test/README.md b/test/README.md
index 0ce3c4e7..45e6d22a 100644
--- a/test/README.md
+++ b/test/README.md
@@ -40,10 +40,10 @@ output.log  # the captured printed output--only for errors
 To add a test, create a new C file in [`src/misc`]:
 
 ```c
-// filter.py(TARGET_TRIPLE): !wasm32-wasip2
-// add-flags.py(CFLAGS): ...
-// add-flags.py(LDFLAGS): ...
-// add-flags.py(RUN): ...
+//! filter.py(TARGET_TRIPLE): !wasm32-wasip2
+//! add-flags.py(CFLAGS): ...
+//! add-flags.py(LDFLAGS): ...
+//! add-flags.py(RUN): ...
 void main() { ... }
 ```
 
diff --git a/test/scripts/add-flags.py b/test/scripts/add-flags.py
index 8a26c46c..643a922b 100755
--- a/test/scripts/add-flags.py
+++ b/test/scripts/add-flags.py
@@ -9,7 +9,7 @@
 # Example:
 # ```
 # $ head one.c
-# // add-flags.py(CFLAGS): -DFOO
+# //! add-flags.py(CFLAGS): -DFOO
 # $ ./add-flags.py CFLAGS one.c
 # -DFOO
 
@@ -19,17 +19,17 @@
 import logging
 
 """
-Match a C comment like the following: `// add-flags.py: <FLAGS>`.
+Match a C comment like the following: `//! add-flags.py: <FLAGS>`.
 """
-PATTERN = re.compile('\\s*//\\s*add-flags\\.py\\(([^)]+)\\):\\s*(.*)')
+PATTERN = re.compile('\\s*//\\!\\s*add-flags\\.py\\(([^)]+)\\):\\s*(.*)')
 
 
 def find_flags(name, file):
     with open(file, 'r') as f:
         for lineno, line in enumerate(f, start=1):
             match = PATTERN.match(line)
-            pos = f'[{file}:{lineno}]'
             if match and match[1] == name:
+                pos = f'[{file}:{lineno}]'
                 logging.debug(f'{pos} found flags')
                 return match[2].strip()
 
diff --git a/test/scripts/filter.py b/test/scripts/filter.py
index 1fb22573..6df11717 100755
--- a/test/scripts/filter.py
+++ b/test/scripts/filter.py
@@ -3,7 +3,7 @@
 # Filter out test files that do not match a configuration variable.
 #
 # This script accepts a list of files as arguments and looks for a comment like
-# the following in each: `// filter.py(<VARIABLE>): <EXPRESSION>`. The
+# the following in each: `//! filter.py(<VARIABLE>): <EXPRESSION>`. The
 # `VARIABLE` value is looked up in the environment and compared with the
 # expression. An `EXPRESSION` is a comma-separated list of terms: either
 # `<string>` or `!<string>`. If the `VARIABLE` value matches the expression, the
@@ -12,9 +12,9 @@
 # Example:
 # ```
 # $ head one.c
-# // filter.py(FOO): bar
+# //! filter.py(FOO): bar
 # $ head two.c
-# // filter.py(FOO):!bar, baz
+# //! filter.py(FOO):!bar, baz
 # $ FOO=bar ./filter.py one.c two.c
 # one.c
 # $ FOO=baz ./filter.py one.c two.c
@@ -55,9 +55,9 @@ def matches_expression(value, expr, pos):
 
 
 """
-Match a C comment like the following: `// filter.py(<VARIABLE>): <EXPRESSION>`.
+Match a C comment like the following: `//! filter.py(<VARIABLE>): <EXPRESSION>`.
 """
-PATTERN = re.compile('\\s*//\\s*filter\\.py\\(([^)]+)\\):\\s*(.*)')
+PATTERN = re.compile('\\s*//\\!\\s*filter\\.py\\(([^)]+)\\):\\s*(.*)')
 
 
 def line_matches(line, env, pos):
diff --git a/test/src/libc-test/functional/argv.c b/test/src/libc-test/functional/argv.c
index 741c7bc2..41dda8ae 100644
--- a/test/src/libc-test/functional/argv.c
+++ b/test/src/libc-test/functional/argv.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/argv.c"
diff --git a/test/src/libc-test/functional/basename.c b/test/src/libc-test/functional/basename.c
index 7549ea45..feb49eef 100644
--- a/test/src/libc-test/functional/basename.c
+++ b/test/src/libc-test/functional/basename.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/basename.c"
diff --git a/test/src/libc-test/functional/clocale_mbfuncs.c b/test/src/libc-test/functional/clocale_mbfuncs.c
index 34b8c4c9..d2bc5752 100644
--- a/test/src/libc-test/functional/clocale_mbfuncs.c
+++ b/test/src/libc-test/functional/clocale_mbfuncs.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/clocale_mbfuncs.c"
diff --git a/test/src/libc-test/functional/clock_gettime.c b/test/src/libc-test/functional/clock_gettime.c
index 2ef8ac0b..1744dfb7 100644
--- a/test/src/libc-test/functional/clock_gettime.c
+++ b/test/src/libc-test/functional/clock_gettime.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/clock_gettime.c"
diff --git a/test/src/libc-test/functional/crypt.c b/test/src/libc-test/functional/crypt.c
index d0792772..a49662cd 100644
--- a/test/src/libc-test/functional/crypt.c
+++ b/test/src/libc-test/functional/crypt.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/crypt.c"
diff --git a/test/src/libc-test/functional/dirname.c b/test/src/libc-test/functional/dirname.c
index 59ba9c75..df9ea4ef 100644
--- a/test/src/libc-test/functional/dirname.c
+++ b/test/src/libc-test/functional/dirname.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/dirname.c"
diff --git a/test/src/libc-test/functional/env.c b/test/src/libc-test/functional/env.c
index 1da8f66f..9dba36a5 100644
--- a/test/src/libc-test/functional/env.c
+++ b/test/src/libc-test/functional/env.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/env.c"
diff --git a/test/src/libc-test/functional/fnmatch.c b/test/src/libc-test/functional/fnmatch.c
index 6e1eefeb..26ae512e 100644
--- a/test/src/libc-test/functional/fnmatch.c
+++ b/test/src/libc-test/functional/fnmatch.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/fnmatch.c"
diff --git a/test/src/libc-test/functional/iconv_open.c b/test/src/libc-test/functional/iconv_open.c
index ceaedcd1..945c5726 100644
--- a/test/src/libc-test/functional/iconv_open.c
+++ b/test/src/libc-test/functional/iconv_open.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/iconv_open.c"
diff --git a/test/src/libc-test/functional/mbc.c b/test/src/libc-test/functional/mbc.c
index ef540675..7b353ec2 100644
--- a/test/src/libc-test/functional/mbc.c
+++ b/test/src/libc-test/functional/mbc.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/mbc.c"
diff --git a/test/src/libc-test/functional/memstream.c b/test/src/libc-test/functional/memstream.c
index 012d3312..c3fccf3a 100644
--- a/test/src/libc-test/functional/memstream.c
+++ b/test/src/libc-test/functional/memstream.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/memstream.c"
diff --git a/test/src/libc-test/functional/qsort.c b/test/src/libc-test/functional/qsort.c
index 4ecae8a4..ba8debf8 100644
--- a/test/src/libc-test/functional/qsort.c
+++ b/test/src/libc-test/functional/qsort.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/qsort.c"
diff --git a/test/src/libc-test/functional/random.c b/test/src/libc-test/functional/random.c
index 8c452573..b6282112 100644
--- a/test/src/libc-test/functional/random.c
+++ b/test/src/libc-test/functional/random.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/random.c"
diff --git a/test/src/libc-test/functional/search_hsearch.c b/test/src/libc-test/functional/search_hsearch.c
index 8184280b..9a5eb9ad 100644
--- a/test/src/libc-test/functional/search_hsearch.c
+++ b/test/src/libc-test/functional/search_hsearch.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/search_hsearch.c"
diff --git a/test/src/libc-test/functional/search_insque.c b/test/src/libc-test/functional/search_insque.c
index ecc1df24..21bf2cde 100644
--- a/test/src/libc-test/functional/search_insque.c
+++ b/test/src/libc-test/functional/search_insque.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/search_insque.c"
diff --git a/test/src/libc-test/functional/search_lsearch.c b/test/src/libc-test/functional/search_lsearch.c
index f3285a24..e681fb54 100644
--- a/test/src/libc-test/functional/search_lsearch.c
+++ b/test/src/libc-test/functional/search_lsearch.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/search_lsearch.c"
diff --git a/test/src/libc-test/functional/search_tsearch.c b/test/src/libc-test/functional/search_tsearch.c
index 94bf8a80..45804c5a 100644
--- a/test/src/libc-test/functional/search_tsearch.c
+++ b/test/src/libc-test/functional/search_tsearch.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/search_tsearch.c"
diff --git a/test/src/libc-test/functional/snprintf.c b/test/src/libc-test/functional/snprintf.c
index 471351ec..67f64da3 100644
--- a/test/src/libc-test/functional/snprintf.c
+++ b/test/src/libc-test/functional/snprintf.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/snprintf.c"
diff --git a/test/src/libc-test/functional/sscanf.c b/test/src/libc-test/functional/sscanf.c
index 003c1eec..ad63e275 100644
--- a/test/src/libc-test/functional/sscanf.c
+++ b/test/src/libc-test/functional/sscanf.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/sscanf.c"
diff --git a/test/src/libc-test/functional/strftime.c b/test/src/libc-test/functional/strftime.c
index 7b187804..787f7e90 100644
--- a/test/src/libc-test/functional/strftime.c
+++ b/test/src/libc-test/functional/strftime.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/strftime.c"
diff --git a/test/src/libc-test/functional/string.c b/test/src/libc-test/functional/string.c
index 1f8bc987..52e181ef 100644
--- a/test/src/libc-test/functional/string.c
+++ b/test/src/libc-test/functional/string.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/string.c"
diff --git a/test/src/libc-test/functional/string_memcpy.c b/test/src/libc-test/functional/string_memcpy.c
index 868da19d..cfc94784 100644
--- a/test/src/libc-test/functional/string_memcpy.c
+++ b/test/src/libc-test/functional/string_memcpy.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/string_memcpy.c"
diff --git a/test/src/libc-test/functional/string_memmem.c b/test/src/libc-test/functional/string_memmem.c
index 38f2d3a8..d2362c4c 100644
--- a/test/src/libc-test/functional/string_memmem.c
+++ b/test/src/libc-test/functional/string_memmem.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/string_memmem.c"
diff --git a/test/src/libc-test/functional/string_memset.c b/test/src/libc-test/functional/string_memset.c
index a62ca6c0..d5672dac 100644
--- a/test/src/libc-test/functional/string_memset.c
+++ b/test/src/libc-test/functional/string_memset.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/string_memset.c"
diff --git a/test/src/libc-test/functional/string_strchr.c b/test/src/libc-test/functional/string_strchr.c
index 6d20432f..c9c2d269 100644
--- a/test/src/libc-test/functional/string_strchr.c
+++ b/test/src/libc-test/functional/string_strchr.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/string_strchr.c"
diff --git a/test/src/libc-test/functional/string_strcspn.c b/test/src/libc-test/functional/string_strcspn.c
index ab45e8e4..052e1e68 100644
--- a/test/src/libc-test/functional/string_strcspn.c
+++ b/test/src/libc-test/functional/string_strcspn.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/string_strcspn.c"
diff --git a/test/src/libc-test/functional/string_strstr.c b/test/src/libc-test/functional/string_strstr.c
index 3f03f843..f0d2dbc7 100644
--- a/test/src/libc-test/functional/string_strstr.c
+++ b/test/src/libc-test/functional/string_strstr.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/string_strstr.c"
diff --git a/test/src/libc-test/functional/strtod.c b/test/src/libc-test/functional/strtod.c
index f4b43be2..9bb36cff 100644
--- a/test/src/libc-test/functional/strtod.c
+++ b/test/src/libc-test/functional/strtod.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/strtod.c"
diff --git a/test/src/libc-test/functional/strtod_long.c b/test/src/libc-test/functional/strtod_long.c
index a91f4cdd..5779e277 100644
--- a/test/src/libc-test/functional/strtod_long.c
+++ b/test/src/libc-test/functional/strtod_long.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/strtod_long.c"
diff --git a/test/src/libc-test/functional/strtod_simple.c b/test/src/libc-test/functional/strtod_simple.c
index b23d469b..bbd817a1 100644
--- a/test/src/libc-test/functional/strtod_simple.c
+++ b/test/src/libc-test/functional/strtod_simple.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/strtod_simple.c"
diff --git a/test/src/libc-test/functional/strtof.c b/test/src/libc-test/functional/strtof.c
index cfca95da..a5682c13 100644
--- a/test/src/libc-test/functional/strtof.c
+++ b/test/src/libc-test/functional/strtof.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/strtof.c"
diff --git a/test/src/libc-test/functional/strtol.c b/test/src/libc-test/functional/strtol.c
index f5258fe5..b874d302 100644
--- a/test/src/libc-test/functional/strtol.c
+++ b/test/src/libc-test/functional/strtol.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/strtol.c"
diff --git a/test/src/libc-test/functional/strtold.c b/test/src/libc-test/functional/strtold.c
index 7195ef49..8f467fed 100644
--- a/test/src/libc-test/functional/strtold.c
+++ b/test/src/libc-test/functional/strtold.c
@@ -1,3 +1,3 @@
-// add-flags.py(CFLAGS): -I.
-// add-flags.py(LDFLAGS): -lc-printscan-long-double
+//! add-flags.py(CFLAGS): -I.
+//! add-flags.py(LDFLAGS): -lc-printscan-long-double
 #include "build/download/libc-test/src/functional/strtold.c"
diff --git a/test/src/libc-test/functional/swprintf.c b/test/src/libc-test/functional/swprintf.c
index a9d44854..278b177d 100644
--- a/test/src/libc-test/functional/swprintf.c
+++ b/test/src/libc-test/functional/swprintf.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/swprintf.c"
diff --git a/test/src/libc-test/functional/tgmath.c b/test/src/libc-test/functional/tgmath.c
index 3f5f4626..3a9d3c33 100644
--- a/test/src/libc-test/functional/tgmath.c
+++ b/test/src/libc-test/functional/tgmath.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/tgmath.c"
diff --git a/test/src/libc-test/functional/udiv.c b/test/src/libc-test/functional/udiv.c
index 15233d25..162b6002 100644
--- a/test/src/libc-test/functional/udiv.c
+++ b/test/src/libc-test/functional/udiv.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/udiv.c"
diff --git a/test/src/libc-test/functional/wcsstr.c b/test/src/libc-test/functional/wcsstr.c
index ca84a72c..9c5581dd 100644
--- a/test/src/libc-test/functional/wcsstr.c
+++ b/test/src/libc-test/functional/wcsstr.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/wcsstr.c"
diff --git a/test/src/libc-test/functional/wcstol.c b/test/src/libc-test/functional/wcstol.c
index 111bd504..04d19dd1 100644
--- a/test/src/libc-test/functional/wcstol.c
+++ b/test/src/libc-test/functional/wcstol.c
@@ -1,2 +1,2 @@
-// add-flags.py(CFLAGS): -I.
+//! add-flags.py(CFLAGS): -I.
 #include "build/download/libc-test/src/functional/wcstol.c"
diff --git a/test/src/misc/fts.c b/test/src/misc/fts.c
index 850c54c6..1126f9b7 100644
--- a/test/src/misc/fts.c
+++ b/test/src/misc/fts.c
@@ -1,4 +1,4 @@
-// add-flags.py(RUN): --dir fs::/
+//! add-flags.py(RUN): --dir fs::/
 
 /*
  * We modified musl-fts not to use fchdir() and we made FTS_NOCHDIR