diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
index cc7bc37..42bf3cd 100644
--- a/.github/workflows/ruby.yml
+++ b/.github/workflows/ruby.yml
@@ -39,6 +39,8 @@ jobs:
 
   cond:
     runs-on: ubuntu-latest
+    env:
+      SKIP_COVERAGE: x
     steps:
       - uses: actions/checkout@v2
       - uses: ruby/setup-ruby@v1
diff --git a/.gitignore b/.gitignore
index 007c2f6..203cd29 100644
--- a/.gitignore
+++ b/.gitignore
@@ -81,6 +81,8 @@
 
 /Makefile
 /include/Makefile
+/include/kernaux.h
+/include/kernaux/console.h
 
 /examples/*.log
 /examples/*.trs
diff --git a/Makefile.am b/Makefile.am
index eeaf2f6..8e75131 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -6,6 +6,7 @@ AM_CFLAGS = \
 	-Wall \
 	-Wextra \
 	-Wno-cast-function-type \
+	-I$(top_builddir)/include \
 	-I$(top_srcdir)/include
 
 lib_LIBRARIES = libkernaux.a
diff --git a/configure.ac b/configure.ac
index 4ac9833..7ed72b5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -151,11 +151,41 @@ AS_IF([test "$with_libc_strnlen" = yes], [AC_DEFINE([WITH_LIBC_STRNLEN],     [1]
 
 
 
+dnl Architecture
+AS_IF([test "$host_cpu" != i386],         [AC_SUBST([comment_line_asm_i386],     [//])])
+AS_IF([test "$host_cpu" != riscv64],      [AC_SUBST([comment_line_asm_riscv64],  [//])])
+AS_IF([test "$host_cpu" != x86_64],       [AC_SUBST([comment_line_asm_x86_64],   [//])])
+
+dnl Packages (enabled by default)
+AS_IF([test "$with_cmdline"        = no], [AC_SUBST([comment_line_cmdline],      [//])])
+AS_IF([test "$with_console"        = no], [AC_SUBST([comment_line_console],      [//])])
+AS_IF([test "$with_elf"            = no], [AC_SUBST([comment_line_elf],          [//])])
+AS_IF([test "$with_framebuffer"    = no], [AC_SUBST([comment_line_framebuffer],  [//])])
+AS_IF([test "$with_mbr"            = no], [AC_SUBST([comment_line_mbr],          [//])])
+AS_IF([test "$with_multiboot2"     = no], [AC_SUBST([comment_line_multiboot2],   [//])])
+AS_IF([test "$with_ntoa"           = no], [AC_SUBST([comment_line_ntoa],         [//])])
+AS_IF([test "$with_pfa"            = no], [AC_SUBST([comment_line_pfa],          [//])])
+AS_IF([test "$with_printf"         = no], [AC_SUBST([comment_line_printf],       [//])])
+AS_IF([test "$with_units"          = no], [AC_SUBST([comment_line_units],        [//])])
+
+dnl Packages (disabled by default)
+AS_IF([test "$with_libc_atoi"    != yes], [AC_SUBST([comment_line_libc_atoi],    [//])])
+AS_IF([test "$with_libc_isdigit" != yes], [AC_SUBST([comment_line_libc_isdigit], [//])])
+AS_IF([test "$with_libc_isspace" != yes], [AC_SUBST([comment_line_libc_isspace], [//])])
+AS_IF([test "$with_libc_memset"  != yes], [AC_SUBST([comment_line_libc_memset],  [//])])
+AS_IF([test "$with_libc_strcpy"  != yes], [AC_SUBST([comment_line_libc_strcpy],  [//])])
+AS_IF([test "$with_libc_strlen"  != yes], [AC_SUBST([comment_line_libc_strlen],  [//])])
+AS_IF([test "$with_libc_strnlen" != yes], [AC_SUBST([comment_line_libc_strnlen], [//])])
+
+
+
 AM_INIT_AUTOMAKE([1.9 subdir-objects])
 
 AC_CONFIG_FILES([
   Makefile
   include/Makefile
+  include/kernaux.h
+  include/kernaux/console.h
 ])
 
 AC_LANG([C])
diff --git a/include/Makefile.am b/include/Makefile.am
index 5700e1f..591e383 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -1,6 +1,3 @@
-## TODO: <kernaux.h> is partially conditional because other files are
-## TODO: <kernaux/libc.h> and <kernaux/console.h> are partially conditional
-
 nobase_include_HEADERS = \
 	kernaux.h \
 	kernaux/arch/i386.h \
diff --git a/include/kernaux.h b/include/kernaux.h
deleted file mode 100644
index cab5c5a..0000000
--- a/include/kernaux.h
+++ /dev/null
@@ -1,23 +0,0 @@
-/*
-    We don't include <kernaux/asm/*.h> because they
-    contain architecture-specific assembly functions.
-
-    We don't include <kernaux/libc.h> because it may
-    conflict with actual freestanding or hosted libc.
-*/
-
-#include <kernaux/assert.h>
-#include <kernaux/cmdline.h>
-#include <kernaux/console.h>
-#include <kernaux/elf.h>
-#include <kernaux/framebuffer.h>
-#include <kernaux/mbr.h>
-#include <kernaux/multiboot2.h>
-#include <kernaux/ntoa.h>
-#include <kernaux/pfa.h>
-#include <kernaux/printf.h>
-#include <kernaux/units.h>
-
-#include <kernaux/arch/i386.h>
-#include <kernaux/arch/riscv64.h>
-#include <kernaux/arch/x86_64.h>
diff --git a/include/kernaux.h.in b/include/kernaux.h.in
new file mode 100644
index 0000000..8c187d3
--- /dev/null
+++ b/include/kernaux.h.in
@@ -0,0 +1,23 @@
+/*
+    We don't include <kernaux/asm/*.h> because they
+    contain architecture-specific assembly functions.
+
+    We don't include <kernaux/libc.h> because it may
+    conflict with actual freestanding or hosted libc.
+*/
+
+#include <kernaux/assert.h>
+@comment_line_cmdline@#include <kernaux/cmdline.h>
+@comment_line_console@#include <kernaux/console.h>
+@comment_line_elf@#include <kernaux/elf.h>
+@comment_line_framebuffer@#include <kernaux/framebuffer.h>
+@comment_line_mbr@#include <kernaux/mbr.h>
+@comment_line_multiboot2@#include <kernaux/multiboot2.h>
+@comment_line_ntoa@#include <kernaux/ntoa.h>
+@comment_line_pfa@#include <kernaux/pfa.h>
+@comment_line_printf@#include <kernaux/printf.h>
+@comment_line_units@#include <kernaux/units.h>
+
+#include <kernaux/arch/i386.h>
+#include <kernaux/arch/riscv64.h>
+#include <kernaux/arch/x86_64.h>
diff --git a/include/kernaux/console.h b/include/kernaux/console.h.in
similarity index 83%
rename from include/kernaux/console.h
rename to include/kernaux/console.h.in
index b4bb176..afd80c8 100644
--- a/include/kernaux/console.h
+++ b/include/kernaux/console.h.in
@@ -10,7 +10,7 @@ extern "C" {
 void kernaux_console_putc(char c);
 
 void kernaux_console_print(const char *s);
-void kernaux_console_printf(const char *format, ...)
+@comment_line_printf@void kernaux_console_printf(const char *format, ...)
 __attribute__((format(printf, 1, 2)));
 void kernaux_console_puts(const char *s);
 void kernaux_console_write(const char *data, size_t size);
diff --git a/src/libc.c b/src/libc.c
index 0f28b82..9c0991e 100644
--- a/src/libc.c
+++ b/src/libc.c
@@ -12,7 +12,7 @@ int atoi(const char *str)
     while (isspace(*str)) ++str;
     bool is_negative = false;
     switch (*str) {
-    case '-': is_negative = true;
+    case '-': is_negative = true; // fall through
     case '+': ++str;
     }
     int result = 0;