Question

I’m trying to do a simple sprintf like this:

snprintf(dest, maxlen_dest, "%'lu", along);

Note the quote: ' in the string.

This means (according to the manual):

‘ For decimal conversion (i, d, u, f, F, g, G) the output is to be
grouped with thousands’ grouping characters if the locale
information indicates any. Note that many versions of gcc(1) cannot
parse this option and will issue a warning. SUSv2 does not include
%’F.

So when I compile, I get this warning:

../common/utils.c:29: warning: ISO C does not support the ''' printf flag
../common/utils.c:29: warning: ISO C does not support the ''' printf flag

So, my question is: is there a function that “supports the ”’ printf flag” I could use?

I want my output to be like:

51 254 234
 1 424 000
       ...
       ...
       ...

Here’s my Makefile (in case there’s some options I should modify):

CC = gcc 
# -g = all debug options
CFLAGS = -g -I../common -W -Wall -pedantic -std=c99
OBJECTS = o/main.o o/opts.o o/verif_liens_bidirectionnels.o o/ecriture.o o/plugin_utils.o o/plugin_algo_groupes.o ../common/o/cell.o ../common/o/utils.o ../common/o/verif.o ../common/o/lecture.o

gen : $(OBJECTS)
  $(CC) -o gen $(OBJECTS) $(CFLAGS) -lm -lgd -lz

o/main.o : main.c
  $(CC) -o $@ -c main.c $(CFLAGS)

o/opts.o : opts.c opts.h
  $(CC) -o $@ -c opts.c $(CFLAGS)

o/verif_liens_bidirectionnels.o : verif_liens_bidirectionnels.c verif_liens_bidirectionnels.h
  $(CC) -o $@ -c verif_liens_bidirectionnels.c $(CFLAGS)

o/ecriture.o : ecriture.c ecriture.h
  $(CC) -o $@ -c ecriture.c $(CFLAGS)

o/plugin_utils.o : plugin_utils.c plugin_utils.h
  $(CC) -o $@ -c plugin_utils.c $(CFLAGS)

o/plugin_algo_groupes.o : plugin_algo_groupes.c plugin_algo_groupes.h
  $(CC) -o $@ -c plugin_algo_groupes.c $(CFLAGS)

../common/o/cell.o : ../common/cell.c ../common/cell.h
  $(CC) -o $@ -c ../common/cell.c $(CFLAGS)

../common/o/utils.o : ../common/utils.c ../common/utils.h
  $(CC) -o $@ -c ../common/utils.c $(CFLAGS)

../common/o/verif.o : ../common/verif.c ../common/verif.h
  $(CC) -o $@ -c ../common/verif.c $(CFLAGS)

../common/o/lecture.o : ../common/lecture.c ../common/lecture.h
  $(CC) -o $@ -c ../common/lecture.c $(CFLAGS)

clean :
  rm $(OBJECTS)

Answer 1

You could add

../common/o/utils.o : CFLAGS := $(filter-out -pedantic,$(CFLAGS))

to the makefile, which should suppress the warning for the specific file.

If you don’t want to rely on non-standard libc extensions, you’ll have to implement the functionality yourself…