Debugging information in C macros
Hello all,
I was wondering if it is possible to improve the debugging information
generated by gcc when resolving C macros? Just as an example, when I
preprocessed the following C file:
extern int printf (__const char *__restrict __format, ...);
#define my_macro(i) \
do { \
*(i) = 1; \
*(i) += 2; \
} while(0)
int main(void)
{
int i = 0;
printf("i = %d\n", i);
my_macro(&i);
printf("i = %d\n", i);
return 0;
}
I got the following output:
# 1 "test.c"
# 1 ""
# 1 ""
# 1 "test.c"
extern int printf (__const char *__restrict __format, ...);
int main(void)
{
int i = 0;
printf("i = %d\n", i);
do { *(&i) = 1; *(&i) += 2; } while(0);
printf("i = %d\n", i);
return 0;
}
By adding a couple of "#" lines as follows I was able to much improve
the debugging experience:
# 1 "test.c"
# 1 ""
# 1 ""
# 1 "test.c"
extern int printf (__const char *__restrict __format, ...);
int main(void)
{
int i = 0;
printf("i = %d\n", i);
# 4 "test.c"
do {
# 5 "test.c"
*(&i) = 1;
# 6 "test.c"
*(&i) += 2;
# 7 "test.c"
} while(0);
# 14 "test.c"
printf("i = %d\n", i);
return 0;
}
I wonder whether this couldn't be done by the gcc preprocessor? Or does
standards compliance forbid this?
( [ http://gcc.gnu.org/onlinedocs/cpp/Preprocessor-Output.html ] didn't
quite make this clear, and it isn't clear to me whether those "#" lines
are part of the standard.)
Regards,
Michael
RE: Debugging information in C macros
> From: bas...@starynkevitch.net
> On Tue, 10 May 2011 17:33:57 +0200
> Michael T wrote:
> > I was wondering if it is possible to improve the debugging information
> > generated by gcc when resolving C macros? Just as an example, when I
> > preprocessed the following C file:
[...]
> I am not a standard guru, but in my naive view this counts as one
> single logical line (because backslash newline is handled by
> preprocessing), so expansion of that macro invocation should be one
> line also.
>
> Besides, I believe that there are lots of actual C code which depends
> upon that behavior. Code like
> #define my_fatal_at(Msg,Line) do { \
> printf ("%s:%d fatal error: %s\n", __FILE__, Line, Msg); \
> abort (); \
> } while(0);
[...]
Sadly that sounds rather convincing. Thanks for the answer and sorry for the
noise.
Regards,
Michael
RE: Debugging information in C macros
> From: rasel...@hotmail.com
> > From: bas...@starynkevitch.net
> > On Tue, 10 May 2011 17:33:57 +0200
> > Michael T wrote:
> > > I was wondering if it is possible to improve the debugging information
> > > generated by gcc when resolving C macros? Just as an example, when I
> > > preprocessed the following C file:
[...]
> > Besides, I believe that there are lots of actual C code which depends
> > upon that behavior. Code like
> > #define my_fatal_at(Msg,Line) do { \
> > printf ("%s:%d fatal error: %s\n", __FILE__, Line, Msg); \
> > abort (); \
> > } while(0);
[...]
> Sadly that sounds rather convincing. Thanks for the answer and sorry for the
> noise.
Although thinking about it, __FILE__ and __LINE__ are also handled by the
preprocessor, so they need not be affected by "#" lines. I'm sure there must be
a reason though why gcc isn't doing this already.
Regards,
Michael
Bug: GCC riscv building fails at self-tests with specific march
I encountered a bug when trying to build a RISC-V GCC cross-compiler. I believe that the most relevant configure options that I used are: --disable-multilib --with-arch=rv32ia --with-abi=ilp32 However, I can post a full list if needed. I have the GCC git tree located at the path "/home/quantum/devel/git/gcc" and am building it inside the sub-directory "build1". It seems to fail when attempting to build the self-tests. Here is an excerpt from the build output: /home/quantum/devel/git/gcc/build1/./gcc/xgcc -B/home/quantum/devel/git/gcc/build1/./gcc/ -xc -nostdinc /dev/null -S -o /dev/null -fself-test=.././../gcc/testsuite/selftests /home/quantum/devel/git/gcc/build1/./gcc/xgcc -B/home/quantum/devel/git/gcc/build1/./gcc/ -xc++ -nostdinc /dev/null -S -o /dev/null -fself-test=.././../gcc/testsuite/selftests cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension It seems to be trying to build test suites that are in conflict with my march settings. Interestingly, I didn't have this issue when trying to build the release version tagged "releases/gcc-13.2.0". However, I wanted to use some newer features that were only merged less than a month ago. I tried to build the GIT tree and encountered this error. I attempted to bisect the issue and found that it only happens when gcc/DEV-PHASE is set to: experimental I'm not very familar with GCC's build system, but this suggests to me that the tests are only conditionally built on experimental/development codebase snapshots. Michael T. Kloos
Re: Bug: GCC riscv building fails at self-tests with specific march
Sorry for the formatting break. Resending... I encountered a bug when trying to build a RISC-V GCC cross-compiler. I believe that the most relevant configure options that I used are: --disable-multilib --with-arch=rv32ia --with-abi=ilp32 However, I can post a full list if needed. I have the GCC git tree located at the path "/home/quantum/devel/git/gcc" and am building it inside the sub-directory "build1". It seems to fail when attempting to build the self-tests. Here is an excerpt from the build output: /home/quantum/devel/git/gcc/build1/./gcc/xgcc -B/home/quantum/devel/git/gcc/build1/./gcc/ -xc -nostdinc /dev/null -S -o /dev/null -fself-test=.././../gcc/testsuite/selftests /home/quantum/devel/git/gcc/build1/./gcc/xgcc -B/home/quantum/devel/git/gcc/build1/./gcc/ -xc++ -nostdinc /dev/null -S -o /dev/null -fself-test=.././../gcc/testsuite/selftests cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension cc1plus: error: '-mdiv' requires '-march' to subsume the 'M' extension It seems to be trying to build test suites that are in conflict with my march settings. Interestingly, I didn't have this issue when trying to build the release version tagged "releases/gcc-13.2.0". However, I wanted to use some newer features that were only merged less than a month ago. I tried to build the GIT tree and encountered this error. I attempted to bisect the issue and found that it only happens when "gcc/DEV-PHASE" is set to: experimental I'm not very familar with GCC's build system, but this suggests to me that the tests are only conditionally built on experimental/development codebase snapshots. Michael T. Kloos
