Use @file to pass the --cfg flags to rustc (fixes #22)

It also helps to avoid spamming the terminal when doing verbose builds.

Signed-off-by: Finn Behrens <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>

Makefile

@@ -726,7 +726,7 @@ $(KCONFIG_CONFIG):
 # This exploits the 'multi-target pattern rule' trick.
 # The syncconfig should be executed only once to make all the targets.
 # (Note: use the grouped target '&:' when we bump to GNU Make 4.3)
-%/config/auto.conf %/config/auto.conf.cmd %/generated/autoconf.h: $(KCONFIG_CONFIG)
+%/config/auto.conf %/config/auto.conf.cmd %/generated/autoconf.h %/generated/rustc_cfg: $(KCONFIG_CONFIG)
  $(Q)$(MAKE) -f $(srctree)/Makefile syncconfig
 else # !may-sync-config
 # External modules and some install targets need include/generated/autoconf.h

scripts/Makefile.lib

@@ -229,9 +229,9 @@ c_flags = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) \
 RUST_BINDGEN_CFLAGS = $(c_flags) $(KBUILD_CFLAGS_MODULE)
 export RUST_BINDGEN_CFLAGS
 
-rustc_cfg_flags = $(shell sed -nE 's/^(CONFIG_[^=]+)=(y|m)$$/--cfg \1/p' $(srctree)/include/config/auto.conf | xargs)
+KCONFIG_RUSTC_CFG ?= $(srctree)/include/generated/rustc_cfg
 
-rustc_flags = $(_rustc_flags) $(modkern_rustcflags) $(rustc_cfg_flags)
+rustc_flags = $(_rustc_flags) $(modkern_rustcflags) @$(shell readlink -f $(KCONFIG_RUSTC_CFG))
 
 # Passed by cargo
 RUSTFLAGS = $(rustc_flags)

scripts/kconfig/confdata.c

@@ -636,6 +636,56 @@ static struct conf_printer kconfig_printer_cb =
  .print_comment = kconfig_print_comment,
 };
 
+/*
+ * rustc cfg printer
+ *
+ * This printer is used when generating the resulting rustc configuration
+ * after kconfig invocation and `defconfig` files.
+ */
+static void rustc_cfg_print_symbol(FILE *fp, struct symbol *sym, const char *value, void *arg)
+{
+ const char *str;
+
+ switch (sym->type) {
+ case S_INT:
+ case S_HEX:
+ case S_BOOLEAN:
+ case S_TRISTATE:
+ str = sym_escape_string_value(value);
+
+ /*
+ * We don't care about disabled ones, i.e. no need for
+ * what otherwise are "comments" in other printers.
+ */
+ if (*value == 'n')
+ return;
+
+ /*
+ * To have similar functionality to the C macro `IS_ENABLED()`
+ * we provide an empty `--cfg CONFIG_X` here in both `y`
+ * and `m` cases.
+ *
+ * Then, the common `fprintf()` below will also give us
+ * a `--cfg CONFIG_X="y"` or `--cfg CONFIG_X="m"`, which can
+ * be used as the equivalent of `IS_BUILTIN()`/`IS_MODULE()`.
+ */
+ if (*value == 'y' || *value == 'm')
+ fprintf(fp, "--cfg=%s%s\n", CONFIG_, sym->name);
+
+ break;
+ default:
+ str = value;
+ break;
+ }
+
+ fprintf(fp, "--cfg=%s%s=%s\n", CONFIG_, sym->name, str);
+}
+
+static struct conf_printer rustc_cfg_printer_cb =
+{
+ .print_symbol = rustc_cfg_print_symbol,
+};
+
 /*
  * Header printer
  *
@@ -1043,7 +1093,7 @@ int conf_write_autoconf(int overwrite)
  struct symbol *sym;
  const char *name;
  const char *autoconf_name = conf_get_autoconfig_name();
- FILE *out, *out_h;
+ FILE *out, *out_h, *out_rustc_cfg;
  int i;
 
  if (!overwrite && is_present(autoconf_name))
@@ -1064,6 +1114,13 @@ int conf_write_autoconf(int overwrite)
  return 1;
  }
 
+ out_rustc_cfg = fopen(".tmp_rustc_cfg", "w");
+ if (!out_rustc_cfg) {
+ fclose(out);
+ fclose(out_h);
+ return 1;
+ }
+
  conf_write_heading(out, &kconfig_printer_cb, NULL);
  conf_write_heading(out_h, &header_printer_cb, NULL);
 
@@ -1075,9 +1132,11 @@ int conf_write_autoconf(int overwrite)
  /* write symbols to auto.conf and autoconf.h */
  conf_write_symbol(out, sym, &kconfig_printer_cb, (void *)1);
  conf_write_symbol(out_h, sym, &header_printer_cb, NULL);
+ conf_write_symbol(out_rustc_cfg, sym, &rustc_cfg_printer_cb, NULL);
  }
  fclose(out);
  fclose(out_h);
+ fclose(out_rustc_cfg);
 
  name = getenv("KCONFIG_AUTOHEADER");
  if (!name)
@@ -1096,6 +1155,14 @@ int conf_write_autoconf(int overwrite)
  if (rename(".tmpconfig", autoconf_name))
  return 1;
 
+ name = getenv("KCONFIG_RUSTC_CFG");
+ if (!name)
+ name = "include/generated/rustc_cfg";
+ if (make_parent_dir(name))
+ return 1;
+ if (rename(".tmp_rustc_cfg", name))
+ return 1;
+
  return 0;
 }