undefined reference when calling inline function
According to the manual, passing -std=gnu11
enables C99 instead of GNU inline semantics.
This means inline
, static inline
and extern inline
all behave differently. In particular, inline
expects an external definition in a separate translation unit (which you can provide without duplicating the definition - see this answer).
Marco Scannadinari
Updated on November 30, 2020Comments
-
Marco Scannadinari over 3 years
I am getting a really odd error from GCC 4.8.1 with inline functions.
I have two near-identical inline functions defined in header files (
debug.h
anderror.h
) insrc/include/
, with the only difference being what they print - one prefixesDEBUG:
to the message, and the other%s: error: %s
(program name, error message). When defining the functions both inline, and compiling a debug build (so it sets the macroDEBUG=1
), I get lots of undefined reference errors:src/main_debug.o gcc -osrc/main_debug.o src/main.c -c -Wall -Wextra -Wpedantic -std=gnu11 -march=native -Og -g -DCC="\"gcc\"" -DCFLAGS="\"-Wall -Wextra -Wpedantic -std=gnu11 -march=native -Og -g\"" -DDEBUG=1 -DBTCWATCH_VERSION="\"0.0.1\"" src/lib/btcapi_debug.o gcc -osrc/lib/btcapi_debug.o src/lib/btcapi.c -c -Wall -Wextra -Wpedantic -std=gnu11 -march=native -Og -g -DCC="\"gcc\"" -DCFLAGS="\"-Wall -Wextra -Wpedantic -std=gnu11 -march=native -Og -g\"" -DDEBUG=1 src/lib/libbtcapi_debug.a ar rc src/lib/libbtcapi_debug.a src/lib/btcapi_debug.o ranlib src/lib/libbtcapi_debug.a src/lib/cmdlineutils_debug.o gcc -o src/lib/cmdlineutils_debug.o src/lib/cmdlineutils.c -c -Wall -Wextra -Wpedantic -std=gnu11 -march=native -Og -g -DCC="\"gcc\"" -DCFLAGS="\"-Wall -Wextra -Wpedantic -std=gnu11 -march=native -Og -g\"" -DDEBUG=1 src/lib/libcmdlineutils_debug.a ar rc src/lib/libcmdlineutils_debug.a src/lib/cmdlineutils_debug.o ranlib src/lib/libcmdlineutils_debug.a debug gcc -obtcwatch-debug src/main_debug.o -Lsrc/lib/ -lbtcapi_debug -lcmdlineutils_debug -lcurl -ljansson src/main_debug.o: In function `main': /home/marcoms/btcwatch/src/main.c:148: undefined reference to `debug' src/main_debug.o:/home/marcoms/btcwatch/src/main.c:185: more undefined references to `debug' follow collect2: error: ld returned 1 exit status make: *** [debug] Error 1
But changing
debug()
's definition tostatic inline
removes the errors. But I have never received any errors fromerror()
's definition, although its defenition isinline
, and notstatic inline
.The definitions are all in headers (i.e. not prototyped)