build: fix some warnings

guile/meson.build

@@ -25,7 +25,7 @@ compile_scm=configure_file(
   configuration: compile_scm_conf,
   install: false
 )
-run_command('chmod', '+x', compile_scm)
+run_command('chmod', '+x', compile_scm, check: true)
 scm_compiler=join_paths(meson.current_build_dir(), 'compile-scm')
 
 snarf = find_program('guile-snarf')
@@ -34,7 +34,8 @@ snarf_args=['-o', '@OUTPUT@', '@INPUT@', '-I' + meson.current_source_dir() + '/.
 	    '-I' + meson.current_build_dir() + '/..']
 
 pkg_config=find_program('pkg-config')
-snarf_args+=run_command(pkg_config, '--cflags', 'glib-2.0', 'guile-3.0').stdout().strip()
+snarf_args+=run_command(pkg_config, '--cflags', 'glib-2.0', 'guile-3.0',
+                        check:true).stdout().strip()
 snarf_gen=generator(snarf,
 		    output: '@BASENAME@.x',
 		    arguments: snarf_args)

meson.build

@@ -147,9 +147,9 @@ version_texi_data=configuration_data()
 version_texi_data.set('VERSION', meson.project_version())
 version_texi_data.set('EDITION', meson.project_version())
 version_texi_data.set('UPDATED',
-                      run_command('date', '+%d %B %Y').stdout().strip())
+                      run_command('date', '+%d %B %Y', check:true).stdout().strip())
 version_texi_data.set('UPDATEDMONTH',
-                      run_command('date', '+%B %Y').stdout().strip())
+                      run_command('date', '+%B %Y', check:true).stdout().strip())
 
 configure_file(input: 'version.texi.in',
 	       output: 'version.texi',

mu/mu-cmd-server.cc

@@ -92,7 +92,7 @@ output_sexp_stdout(Sexp&& sexp, bool flush = false)
 	}
 
 	if (flush)
-		::fflush(::stdout);
+		std::fflush(stdout);
 }
 
 static void

mu4e/meson.build

@@ -84,7 +84,13 @@ foreach src : mu4e_plain_srcs
 endforeach
 
 
-foreach src : mu4e_all_srcs
+# we'd like to compile mu4e-meta.el, too, but using mu4e_all_srcs here
+# yields:
+# mu4e/meson.build:105: WARNING: Source item '.../mu4e/mu4e-meta.el' cannot be
+# converted to File object, because it is a generated file. This will become a
+# hard error in the future.
+
+foreach src : mu4e_plain_srcs
   target_name= '@BASENAME@.elc'
   target_path = join_paths(meson.current_build_dir(), target_name)
   target_func = '(setq byte-compile-dest-file-function(lambda(_) "' + target_path + '"))'