fix warnings in 9.6, 10, 11's contrib when compiling without openssl

Hello,

after plain ./configure without options (including noticeable absence of 
--with-openssl) and make,
make -C contrib COPT=-Werror gives error with gcc-11 on REL_9_6_STABLE, 
REL_10_STABLE or REL_11_STABLE.

The warning/error is about misleading indent in 
contrib/pgcrypto/imath.c's CLAMP macro:

imath.c: In function ‘mp_int_add’:
imath.c:133:1: error: this ‘while’ clause does not guard... 
[-Werror=misleading-indentation]
   133 | while(uz_ > 1 && (*dz_-- == 0)) --uz_;MP_USED(z_)=uz_;}while(0)
       | ^~~~~
imath.c:670:17: note: in expansion of macro ‘CLAMP’
   670 |                 CLAMP(c);
       |                 ^~~~~
In file included from imath.c:34:
imath.h:68:26: note: ...this statement, but the latter is misleadingly 
indented as if it were guarded by the ‘while’
    68 | #define MP_USED(Z)       ((Z)->used)
       |                          ^
imath.c:133:39: note: in expansion of macro ‘MP_USED’
   133 | while(uz_ > 1 && (*dz_-- == 0)) --uz_;MP_USED(z_)=uz_;}while(0)
       |                                       ^~~~~~~
imath.c:670:17: note: in expansion of macro ‘CLAMP’
   670 |                 CLAMP(c);
       |                 ^~~~~

pgcrypto-fix-imath-clamp-warning.patch, attached, is a suggested minimal 
fix:
diff --git a/contrib/pgcrypto/imath.c b/contrib/pgcrypto/imath.c
index b94a51b81a4..801b843cbe3 100644
--- a/contrib/pgcrypto/imath.c
+++ b/contrib/pgcrypto/imath.c
@@ -130,7 +130,8 @@ do{T *u_=(A),*v_=u_+(N)-1;while(u_<v_){T 
xch=*u_;*u_++=*v_;*v_--=xch;}}while(0)
  #else
  #define CLAMP(Z) \
  do{mp_int z_=(Z);mp_size uz_=MP_USED(z_);mp_digit 
*dz_=MP_DIGITS(z_)+uz_-1;\
-while(uz_ > 1 && (*dz_-- == 0)) --uz_;MP_USED(z_)=uz_;}while(0)
+while(uz_ > 1 && (*dz_-- == 0)) --uz_;\
+MP_USED(z_)=uz_;}while(0)
  #endif

  #undef MIN

The same patch works for all 9.6, 10 and 11. It's not needed in 12 or 
later, they compile without warnings just fine even without --with-openssl.

In addition, 9.6 (unlike 10 and 11) gives four "array-parameter=" 
warnings about contrib/pgcrypto/sha2.c:

sha2.c:552:20: error: argument 1 of type ‘uint8[]’ {aka ‘unsigned 
char[]’} with mismatched bound [-Werror=array-parameter=]
   552 | SHA256_Final(uint8 digest[], SHA256_CTX *context)
       |              ~~~~~~^~~~~~~~
In file included from sha2.c:44:
sha2.h:93:30: note: previously declared as ‘uint8[32]’ {aka ‘unsigned 
char[32]’}
    93 | void            SHA256_Final(uint8[SHA256_DIGEST_LENGTH], 
SHA256_CTX *);
       |                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~

and the same for SHA{512,384,224}_Final.

pgcrypto-fix-sha2-warning.patch, attached, is a suggested minimal fix 
for that:
  void
-SHA256_Final(uint8 digest[], SHA256_CTX *context)
+SHA256_Final(uint8 digest[SHA256_DIGEST_LENGTH], SHA256_CTX *context)
  {
etc.

Please consider fixing those warnings.

-- 
Anton Voloshin
Postgres Professional, The Russian Postgres Company
https://postgrespro.ru