public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "hongbo dot yang at mathworks dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/35774] New: wrong code on casting int result to signed char Date: Mon, 31 Mar 2008 14:34:00 -0000 [thread overview] Message-ID: <bug-35774-15992@http.gcc.gnu.org/bugzilla/> (raw) In the main function there is a cast casting int result to signed char. typedef int int32_T; typedef unsigned int uint32_T; typedef signed char int8_T; #include <stdio.h> int main(void) { int32_T i; uint32_T numerator; for (i = 126; i < 256; i++) { numerator = (uint32_T)((int8_T)(-128 + i) + 128) * 63U; fprintf(stdout, "i = %d numerator = %u\n", i, numerator); } return numerator; } This program is compiled with gcc -O0 -g, I suppose the result of the variable "numerator" should be: 126 * 63 127 * 63 128 * 63 .... But the printed result is equal to: 126 * 63 127 * 63 - 128 * 63 .... The generated assembly code on mac with Intel Core-2-Duo processor is: movl -24(%ebp), %eax movsbl %al,%edx movl %edx, %eax sall $6, %eax subl %edx, %eax movl %eax, -20(%ebp) It seems both -128 and +128 are ignored. This problem doesn't appear on gcc 4.1.1. -- Summary: wrong code on casting int result to signed char Product: gcc Version: 4.0.1 Status: UNCONFIRMED Severity: major Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: hongbo dot yang at mathworks dot com GCC build triplet: i686-linux-gnu GCC host triplet: i686-linux-gnu GCC target triplet: i686-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35774
next reply other threads:[~2008-03-31 14:34 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2008-03-31 14:34 hongbo dot yang at mathworks dot com [this message] 2008-03-31 16:10 ` [Bug c/35774] " rguenth at gcc dot gnu dot org
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=bug-35774-15992@http.gcc.gnu.org/bugzilla/ \ --to=gcc-bugzilla@gcc.gnu.org \ --cc=gcc-bugs@gcc.gnu.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).