David Malcolm <dmalc...@redhat.com> writes: > On Tue, 2024-11-26 at 16:35 -0500, Marek Polacek wrote: >> On Mon, Nov 25, 2024 at 10:49:02PM -0500, David Malcolm wrote: >> > This patch attempts to provide better error messages for >> > code compiled with C23 that hasn't been updated for >> > "bool", "true", and "false" becoming keywords (based on >> > a brief review of the Gentoo bug tracker links given at >> > https://gcc.gnu.org/pipermail/gcc/2024-November/245185.html). >> > >> > Specifically: >> > >> > (1) with "typedef int bool;" previously we emitted: >> > >> > t1.c:7:13: error: two or more data types in declaration specifiers >> > 7 | typedef int bool; >> > | ^~~~ >> > t1.c:7:1: warning: useless type name in empty declaration >> > 7 | typedef int bool; >> > | ^~~~~~~ >> > >> > whereas with this patch we emit: >> > >> > t1.c:7:13: error: 'bool' cannot be defined via 'typedef' >> > 7 | typedef int bool; >> > | ^~~~ >> > t1.c:7:13: note: 'bool' is a keyword with '-std=c23' onwards >> > t1.c:7:1: warning: useless type name in empty declaration >> > 7 | typedef int bool; >> > | ^~~~~~~ >> > >> > (2) with "int bool;" previously we emitted: >> > >> > t2.c:7:5: error: two or more data types in declaration specifiers >> > 7 | int bool; >> > | ^~~~ >> > t2.c:7:1: warning: useless type name in empty declaration >> > 7 | int bool; >> > | ^~~ >> > >> > whereas with this patch we emit: >> > >> > t2.c:7:5: error: 'bool' cannot be used here >> > 7 | int bool; >> > | ^~~~ >> > t2.c:7:5: note: 'bool' is a keyword with '-std=c23' onwards >> > t2.c:7:1: warning: useless type name in empty declaration >> > 7 | int bool; >> > | ^~~ >> > >> > (3) with "typedef enum { false = 0, true = 1 } _Bool;" previously >> > we >> > emitted: >> > >> > t3.c:7:16: error: expected identifier before 'false' >> > 7 | typedef enum { false = 0, true = 1 } _Bool; >> > | ^~~~~ >> > t3.c:7:38: error: expected ';', identifier or '(' before '_Bool' >> > 7 | typedef enum { false = 0, true = 1 } _Bool; >> > | ^~~~~ >> > t3.c:7:38: warning: useless type name in empty declaration >> > >> > whereas with this patch we emit: >> > >> > t3.c:7:16: error: cannot use keyword 'false' as enumeration >> > constant >> > 7 | typedef enum { false = 0, true = 1 } _Bool; >> > | ^~~~~ >> > t3.c:7:16: note: 'false' is a keyword with '-std=c23' onwards >> > t3.c:7:38: error: expected ';', identifier or '(' before '_Bool' >> > 7 | typedef enum { false = 0, true = 1 } _Bool; >> > | ^~~~~ >> > t3.c:7:38: warning: useless type name in empty declaration >> > >> > >> > Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu. >> > OK for trunk? >> >> Thanks for the patch. >> >> For: >> >> typedef int _Bool; >> >> or >> >> int _Bool; >> >> this patch says: >> >> note: '_Bool' is a keyword with '-std=c23' onwards >> >> but I don't think that's true: _Bool was added in C99 and is >> obsolescent in >> C23. > > Is _Bool meant to be usable in c90? > > I tried with -std=c90 and it fails; see: > https://godbolt.org/z/Wf6a9EKP9
No, it's not: it was introducd in C99. > > <source>:1:13: error: two or more data types in declaration specifiers > 1 | typedef int _Bool; > | ^~~~~ > <source>:1:1: warning: useless type name in empty declaration > 1 | typedef int _Bool; > | ^~~~~~~ > > Thanks > Dave
