From 2475d37ac30b8a850d3dd4fcbcb20895928b73fd Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Wed, 23 Mar 2022 08:18:07 +0100 Subject: [PATCH] tools/nolibc/stdlib: only reference the external environ when inlined When building with gcc at -O0 we're seeing link errors due to the "environ" variable being referenced by getenv(). The problem is that at -O0 gcc will not inline getenv() and will not drop the external reference. One solution would be to locally declare the variable as weak, but then it would appear in all programs even those not using it, and would be confusing to users of getenv() who would forget to set environ to envp. An alternate approach used in this patch consists in always inlining the outer part of getenv() that references this extern so that it's always dropped when not used. The biggest part of the function was now moved to a new function called _getenv() that's still not inlined by default. Reported-by: Ammar Faizi Signed-off-by: Willy Tarreau Tested-by: Ammar Faizi Signed-off-by: Paul E. McKenney --- tools/include/nolibc/stdlib.h | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/tools/include/nolibc/stdlib.h b/tools/include/nolibc/stdlib.h index aca8616335e371..8a07e263f0d02d 100644 --- a/tools/include/nolibc/stdlib.h +++ b/tools/include/nolibc/stdlib.h @@ -60,16 +60,17 @@ int atoi(const char *s) return atol(s); } -/* Tries to find the environment variable named in the environment array - * pointed to by global variable "environ" which must be declared as a char **, - * and must be terminated by a NULL (it is recommended to set this variable to - * the "envp" argument of main()). If the requested environment variable exists - * its value is returned otherwise NULL is returned. +/* getenv() tries to find the environment variable named in the + * environment array pointed to by global variable "environ" which must be + * declared as a char **, and must be terminated by a NULL (it is recommended + * to set this variable to the "envp" argument of main()). If the requested + * environment variable exists its value is returned otherwise NULL is + * returned. getenv() is forcefully inlined so that the reference to "environ" + * will be dropped if unused, even at -O0. */ static __attribute__((unused)) -char *getenv(const char *name) +char *_getenv(const char *name, char **environ) { - extern char **environ; int idx, i; if (environ) { @@ -83,6 +84,13 @@ char *getenv(const char *name) return NULL; } +static inline __attribute__((unused,always_inline)) +char *getenv(const char *name) +{ + extern char **environ; + return _getenv(name, environ); +} + /* Converts the unsigned long integer to its hex representation into * buffer , which must be long enough to store the number and the * trailing zero (17 bytes for "ffffffffffffffff" or 9 for "ffffffff"). The