On Thu, 2016-01-28 at 11:12 -0800, Steve Ellcey wrote: > David, > > This patch has broken the top-of-tree glibc build
Bother; sorry. FWIW, I'm about to get on a plane (for FOSDEM), so I'm not in a great position to tackle this yet. > I get an error on an > undef that is supposed to be protected by Pragmas. It happens when > compiling intl/plural.c in glibc. I created a preprocessed source > file > but when I compile it, the error doesn't happen. PR preprocessor/69126 was all about the location of where _Pragma macros expand to, so it would make sense that you might see different behaviors with -save-temps. > I will try to create a > small unpreprocessed standalone test case but maybe this is enough > for > you to know what is happening. > > If I look at the preprocessed code, the statement in question is > under ingore warning pragmas. > > #pragma GCC diagnostic push > #pragma GCC diagnostic ignored "-Wuninitialized" > #pragma GCC diagnostic ignored "-Wmaybe-uninitialized" > *++yyvsp = __gettextlval; > #pragma GCC diagnostic pop > > > Steve Ellcey > sell...@imgtec.com > > plural.c: In function '__gettextparse': > plural.c:1767:12: error: '__gettextlval.num' may be used > uninitialized > in this function [-Werror=maybe-uninitialized] > *++yyvsp = yylval; > > plural.c:66:25: note: '__gettextlval.num' was declared here > #define yylval __gettextlval > ^ > plural.c:1265:9: note: in expansion of macro 'yylval' > YYSTYPE yylval YY_INITIAL_VALUE(yyval_default); > ^~~~~~ > cc1: all warnings being treated as errors Code in question appears to be here: https://sourceware.org/git/?p=glibc.git;a=blob;f=intl/plural.c;h=a94af3 c542b1aeadebbe02d67dabd2d535f70726;hb=HEAD#l1767 1766 YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN 1767 *++yyvsp = yylval; 1768 YY_IGNORE_MAYBE_UNINITIALIZED_END Macro itself is defined at line 1244: 1244 # define YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN \ 1245 _Pragma ("GCC diagnostic push") \ 1246 _Pragma ("GCC diagnostic ignored \"-Wuninitialized\"")\ 1247 _Pragma ("GCC diagnostic ignored \"-Wmaybe-uninitialized\"") 1248 # define YY_IGNORE_MAYBE_UNINITIALIZED_END \ 1249 _Pragma ("GCC diagnostic pop") Maybe there's an issue with having a _Pragma inside another macro; my hunch would be that my patch is making it use the location of the _Pragma within the *definition* of the YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN/END macros, rather than their expansion. But that's just a hunch at this stage. I think I have a minimal reproducer: $ cat /tmp/test.c # define YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN \ _Pragma ("GCC diagnostic push") \ _Pragma ("GCC diagnostic ignored \"-Wuninitialized\"")\ _Pragma ("GCC diagnostic ignored \"-Wmaybe-uninitialized\"") # define YY_IGNORE_MAYBE_UNINITIALIZED_END \ _Pragma ("GCC diagnostic pop") void test (char yylval) { char *yyvsp; YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN *++yyvsp = yylval; YY_IGNORE_MAYBE_UNINITIALIZED_END } $ ./xgcc -B. -c /tmp/test.c -Wall /tmp/test.c: In function ‘test’: /tmp/test.c:12:12: warning: ‘yyvsp’ is used uninitialized in this function [-Wuninitialized] *++yyvsp = yylval; ~~~~~~~~~^~~~~~~~ $ ./xgcc -B. -c /tmp/test.c -save-temps $ ./xgcc -B. -c test.i -Wall (compiles with no warnings)
