C99 conforming static assert

[torben-hansen]

Issues:

CryptoAlg-611

Description of changes:

_Static_assert and static_assert are defined in C11 and does not conform to C99. This change implements a static assertion mechanism that conforms to C99. It is inspired by similar implementations in:

• AWS-C-COMMON https://github.com/awslabs/aws-c-common/blob/a61f2ea5fbc9ac2eee9fe32f7a3fdbd399d9fbdb/include/aws/common/macros.h#L16
• Perl: https://github.com/Perl/perl5/blob/5640a370e8b19af74b8ca0b4694464c21a87916b/perl.h#L3862

In addition, I attempted to improve the robustness of the C99 violation test.

Main changes are in:

• include/openssl/type_check.h
• tests/coding_guidelines/c99_gcc_test.sh

Call-outs:

The second argument to OPENSSL_STATIC_ASSERT used to be a string literal. We cannot "unstringify" to construct a valid token. So, I had to replace all strings with tokens in the code base. The variable name of the typedefe'd struct should be unique to avoid shadowing already defined types.

Testing:

There are no run-time changes.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[nebeid]

Would it be possible add to an example of what an assertion error looks like? That, I think, would help in understanding the final output of all the macro definitions.

[torben-hansen]

Changing

OPENSSL_STATIC_ASSERT(sizeof(((EVP_AEAD_CTX *)NULL)->state) >=
                          sizeof(struct aead_aes_gcm_ctx),
                      AEAD_state_is_too_small)

to

OPENSSL_STATIC_ASSERT(sizeof(((EVP_AEAD_CTX *)NULL)->state) <
                          sizeof(struct aead_aes_gcm_ctx),
                      AEAD_state_is_too_small)

produces the following compile-time error:

../crypto/../include/openssl/type_check.h:85:35: error: negative width in bit-field ‘static_assertion_at_line_913_error_is_AEAD_state_is_too_small’
         unsigned int AWSLC_CONCAT(static_assertion_, msg) : (cond) ? 1 : - 1; \
                                   ^
../crypto/../include/openssl/type_check.h:83:35: note: in definition of macro ‘AWSLC_CONCAT
’
 #define AWSLC_CONCAT(left, right) left##right
                                   ^~~~
../crypto/../include/openssl/type_check.h:87:53: note: in expansion of macro ‘AWSLC_STATIC_ASSERT_DEFINE’
 #define AWSLC_STATIC_ASSERT_ADD_LINE0(cond, suffix) AWSLC_STATIC_ASSERT_DEFINE(cond, AWSLC_CONCAT(at_line_, suffix))
                                                     ^~~~~~~~~~~~~~~~~~~~~~~~~~
../crypto/../include/openssl/type_check.h:88:59: note: in expansion of macro ‘AWSLC_STATIC_ASSERT_ADD_LINE0’
 #define AWSLC_STATIC_ASSERT_ADD_LINE1(cond, line, suffix) AWSLC_STATIC_ASSERT_ADD_LINE0(cond, AWSLC_CONCAT(line, suffix))
                                                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../crypto/../include/openssl/type_check.h:89:53: note: in expansion of macro ‘AWSLC_STATIC_ASSERT_ADD_LINE1’
 #define AWSLC_STATIC_ASSERT_ADD_LINE2(cond, suffix) AWSLC_STATIC_ASSERT_ADD_LINE1(cond, __LINE__, suffix)
                                                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../crypto/../include/openssl/type_check.h:90:53: note: in expansion of macro ‘AWSLC_STATIC_ASSERT_ADD_LINE2’
 #define AWSLC_STATIC_ASSERT_ADD_ERROR(cond, suffix) AWSLC_STATIC_ASSERT_ADD_LINE2(cond, AWSLC_CONCAT(_error_is_, suffix))
                                                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../crypto/../include/openssl/type_check.h:91:44: note: in expansion of macro ‘AWSLC_STATIC_ASSERT_ADD_ERROR’
 #define OPENSSL_STATIC_ASSERT(cond, error) AWSLC_STATIC_ASSERT_ADD_ERROR(cond, error);
                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../crypto/fipsmodule/cipher/e_aes.c:911:1: note: in expansion of macro ‘OPENSSL_STATIC_ASSERT’
 OPENSSL_STATIC_ASSERT(sizeof(((EVP_AEAD_CTX *)NULL)->state) <