迁移至RHEL 9后Oracle Pro*C++编译#if __has_include报错排查

问题背景 #

将开发环境迁移到RHEL 9并升级新版GNU编译器后，老旧Pro*C++代码编译失败，报错核心涉及#if __has_include(<sys/single_threaded.h>)预处理指令。尝试谷歌搜索、Copilot辅助排查及Oracle官方支持均未找到有效方案，即使简化测试代码后仍出现异常语法错误。

复现信息 #

简化测试代码 #

#include <stdio.h>
#if __has_include(<sys/single_threaded.h>)
#include <sys/single_threaded.h>
#endif

EXEC SQL BEGIN DECLARE SECTION;
    int emp_id;
EXEC SQL END DECLARE SECTION;

int main() {
    EXEC SQL CONNECT :user IDENTIFIED BY :pass;
    printf("Test\n");
    return 0;
}

编译脚本 #

proc in=test.pc out=test.c code=cpp parse=full
g++ -c test.c -o test.o

完整报错输出 #

Pro*C/C++: Release 19.0.0.0.0 - Production on Tue Aug 22 10:00:00 2023
Version 19.19.0.0.0

Copyright (c) 1982, 2023, Oracle and/or its affiliates.  All rights reserved.

System default option values taken from: /opt/oracle/product/19c/dbhome_1/precomp/admin/pcscfg.cfg

test.pc:2: Error: PCC-S-02015, Encountered the symbol "__has_include" when expecting one of the following:

   ( begin case declare else elsif end exception for goto if loop mod
   null pragma raise return select update while with <an identifier>
   <a double-quoted string> a bind variable << continue close current
   delete fetch lock insert open rollback savepoint set sql execute
   commit forall merge pipe purge
The symbol "if" was substituted for "__has_include" to continue.

test.pc:2: Error: PCC-S-02007, Syntax error at or near line 2, column 6

排查思路 #

1. 逐步简化代码后确认：只要包含__has_include相关预处理指令，ProC预处理阶段就会报错，说明ProC的预处理器不支持GCC的__has_include扩展宏。
2. 验证ORA_PROC宏特性：ProC在预处理代码时会自动定义ORA_PROC宏，可用于区分ProC预处理和后续GCC编译阶段。

解决方案 #

用#ifndef ORA_PROC包裹包含__has_include的代码块，让Pro*C预处理阶段跳过不支持的代码，由后续GCC编译器处理：

#include <stdio.h>
#ifndef ORA_PROC
#if __has_include(<sys/single_threaded.h>)
#include <sys/single_threaded.h>
#endif
#endif

EXEC SQL BEGIN DECLARE SECTION;
    int emp_id;
EXEC SQL END DECLARE SECTION;

int main() {
    EXEC SQL CONNECT :user IDENTIFIED BY :pass;
    printf("Test\n");
    return 0;
}

重新执行编译脚本即可正常通过编译。

内容的提问来源于stack exchange，提问作者EvilTeach