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From: "goran dot steen at enea dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/40397] New: Variable values calculated differently depending on storage class Date: Wed, 10 Jun 2009 11:11:00 -0000 [thread overview] Message-ID: <bug-40397-17819@http.gcc.gnu.org/bugzilla/> (raw) /************* CODE EXAMPLE ***************/ #include <stdio.h> #include <string.h> typedef unsigned int U32; typedef unsigned short U16; typedef unsigned char U8; #ifndef __GNUC__ #define __attribute__(a) #endif /* __GNUC__ */ #define APP6DR_PACK_STRUCT __attribute__((packed)) #define APP6DR_INLINE_FUNC(func) \ __inline__ func __attribute__((always_inline)); \ extern __inline__ __attribute__((gnu_inline)) func struct app6drIpHdr { unsigned int ip_v :4; unsigned int ip_hl :4; U8 ip_tos; U16 ip_len; U16 ip_id; U16 ip_off; U8 ip_ttl; U8 ip_p; U16 ip_sum; struct { U32 ip_sa; U32 ip_da; } ip_addr_r; } APP6DR_PACK_STRUCT; typedef struct app6drIpHdr App6drIpHdr; #define APP6DR_CALC_CSUM(hdr_p,len,cs) App6dr_calcCs16((const char*)(hdr_p), (len), &(cs)) APP6DR_INLINE_FUNC(void App6dr_calcCs16(const char* hdr_p, U32 len, volatile U16* cs_p)) { U32 i, sum; for(i=0, sum=0; i<(len)/2; i++) { U32 val = ((U32*)hdr_p)[i]; sum += ((val&0xffff) + (val>>16)); } if ((len) & 1) sum += ((U16*)hdr_p)[(len)-1]; while(sum>>16) sum = (sum&0xffff)+(sum>>16); *cs_p = (U16)(~sum); } #define APP6DR_CALC_IPV4_CSUM(ipv4_p) \ (ipv4_p)->ip_sum = 0x0000; \ APP6DR_CALC_CSUM((char*)(ipv4_p),sizeof(App6drIpHdr)/2,(ipv4_p)->ip_sum) #define DOIT() \ memset((void*)&iph, 0xfe, sizeof(App6drIpHdr)); \ iph.ip_v = 4; \ iph.ip_hl = 5; \ iph.ip_tos = 0; \ iph.ip_len = 0; \ iph.ip_id = 0; \ iph.ip_off = 0; \ iph.ip_ttl = 64; /* XXX */ \ iph.ip_p = 50; /* ESP */ \ iph.ip_addr_r.ip_sa = (U32) sa; \ iph.ip_addr_r.ip_da = (U32) da; \ APP6DR_CALC_IPV4_CSUM(&iph);\ fprintf(stderr, "checksum = 0x%04x\n", iph.ip_sum); void testchksum2(U32 sa, U32 da) { static App6drIpHdr iph; DOIT(); } void testchksum1(U32 sa, U32 da) { App6drIpHdr iph; DOIT(); } int main() { testchksum1(0x0a0a0a14, 0x0a0a0a01); testchksum2(0x0a0a0a14, 0x0a0a0a01); return 0; } /************ END OF CODE EXAMPLE **************/ Compiled with gcc -Os -Wall -pedantic main.c -o runme Output: checksum = 0xa89c checksum = 0xa542 The only difference between outputs are that the variables made calculations on have different storage classes, ie automatic and static. -- Summary: Variable values calculated differently depending on storage class Product: gcc Version: 4.2.3 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: goran dot steen at enea dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40397
next reply other threads:[~2009-06-10 11:11 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2009-06-10 11:11 goran dot steen at enea dot com [this message] 2009-06-10 12:43 ` [Bug c/40397] " goran dot steen at enea dot com
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