| Message ID | 20220815031551.775444-1-joel@joelfernandes.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 5c375b0d061174c597748c058e60670adac67232 |
| Headers | show |
| Series | libtraceevent: Fixing linking to C++ code | expand |
On Sun, 14 Aug 2022 23:15:51 -0400 "Joel Fernandes (Google)" <joel@joelfernandes.org> wrote: > Linking in C++ compilers (including g++) causes references to be created > with their arguments. Due to this, trace library headers included into > C++ code base will cause their objects to built with symbols with > arguments. Apparently this is to support operator overloading in C++. > > This causes linker errors. For example, here's what I get when I try to > link libtraceevent with a main.o built from a C++ main.cc source file. > > main.cc:(.text+0x90): > undefined reference to `trace_seq_init(trace_seq*)' > undefined reference to `trace_seq_do_printf(trace_seq*)' > undefined reference to `tep_event_fields(tep_event*)' > > The standard fix for this is to wrap the C project's header in > extern "C". > > With this patch, I am able to link libtraceevent into a C++ > code base. > > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> > --- Applied. Thanks Joel! -- Steve
diff --git a/include/traceevent/event-parse.h b/include/traceevent/event-parse.h index 0b911e1..9d7634e 100644 --- a/include/traceevent/event-parse.h +++ b/include/traceevent/event-parse.h @@ -14,6 +14,10 @@ #include "trace-seq.h" +#ifdef __cplusplus +extern "C" { +#endif + #ifndef __maybe_unused #define __maybe_unused __attribute__((unused)) #endif @@ -778,4 +782,8 @@ void tep_set_loglevel(enum tep_loglevel level); void tep_print_field(struct trace_seq *s, void *data, struct tep_format_field *field); +#ifdef __cplusplus +} +#endif + #endif /* _PARSE_EVENTS_H */ diff --git a/include/traceevent/trace-seq.h b/include/traceevent/trace-seq.h index d68ec69..217492f 100644 --- a/include/traceevent/trace-seq.h +++ b/include/traceevent/trace-seq.h @@ -10,6 +10,10 @@ #include <stdarg.h> #include <stdio.h> +#ifdef __cplusplus +extern "C" { +#endif + /* ----------------------- trace_seq ----------------------- */ #ifndef TRACE_SEQ_BUF_SIZE @@ -52,4 +56,8 @@ extern void trace_seq_terminate(struct trace_seq *s); extern int trace_seq_do_fprintf(struct trace_seq *s, FILE *fp); extern int trace_seq_do_printf(struct trace_seq *s); +#ifdef __cplusplus +} +#endif + #endif /* _TRACE_SEQ_H */
Linking in C++ compilers (including g++) causes references to be created with their arguments. Due to this, trace library headers included into C++ code base will cause their objects to built with symbols with arguments. Apparently this is to support operator overloading in C++. This causes linker errors. For example, here's what I get when I try to link libtraceevent with a main.o built from a C++ main.cc source file. main.cc:(.text+0x90): undefined reference to `trace_seq_init(trace_seq*)' undefined reference to `trace_seq_do_printf(trace_seq*)' undefined reference to `tep_event_fields(tep_event*)' The standard fix for this is to wrap the C project's header in extern "C". With this patch, I am able to link libtraceevent into a C++ code base. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> --- include/traceevent/event-parse.h | 8 ++++++++ include/traceevent/trace-seq.h | 8 ++++++++ 2 files changed, 16 insertions(+)